Uplink listen-before-talk failure recovery

ABSTRACT

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may identify a bandwidth part (BWP) to switch to after identifying consistent uplink listen-before-talk (LBT) failures on a first BWP based on parameters indicated by a base station. For example, the base station may transmit a switching parameter to the UE that the UE then uses to switch to a second BWP based on identifying the consistent uplink LBT failures on the first BWP. Subsequently, after selecting the second BWP, the UE may attempt to use the second BWP for uplink transmissions (e.g., after performing a random access procedure). Additionally, the UE may indicate the consistent uplink LBT failures to a base station associated with the failed BWP based on a type of cell that is using that failed BWP.

CROSS REFERENCE

The present application for patent claims the benefit of U.S.Provisional Patent Application No. 62/932,321 by OZTURK et al., entitled“UPLINK LISTEN-BEFORE-TALK FAILURE RECOVERY,” filed Nov. 7, 2019,assigned to the assignee hereof, and expressly incorporated by referenceherein.

FIELD OF TECHNOLOGY

The following relates generally to wireless communications and morespecifically to uplink listen-before-talk (LBT) failure recovery.

BACKGROUND

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform spread orthogonal frequency division multiplexing(DFT-S-OFDM). A wireless multiple-access communications system mayinclude one or more base stations or one or more network access nodes,each simultaneously supporting communication for multiple communicationdevices, which may be otherwise known as user equipment (UE).

In some cases, a UE and a base station may communicate on resources ofan unlicensed band (e.g., NR unlicensed (NR-U) frequency bands). Forexample, the resources of the unlicensed band may be shared amongmultiple UEs (e.g., and multiple base stations), such that a UE maycontend for one or more of these shared resources to communicate withthe base station (e.g., performing contention-based procedures, such asa contention based random access procedure). Accordingly, a UE may checkwhether a channel in the unlicensed band (e.g., a set of frequencyresources) is clear prior to attempting to communicate with a basestation. In some cases, this check of whether the channel is clear mayinclude a listen-before-talk (LBT) procedure, where the UE listens tothe channel to determine whether any on-going transmissions areoccurring prior to transmitting an uplink message to the base station(e.g., whether the channel is occupied or not prior to transmitting).

SUMMARY

The described techniques relate to improved methods, systems, devices,and apparatuses that support uplink listen-before-talk (LBT) failurerecovery. Generally, the described techniques provide for a userequipment (UE) to receive a switching parameter from a base stationindicating how the UE should react when consistent LBT failures areidentified for a first bandwidth part (BWP). For example, the UE may useinformation conveyed in the switching parameter to switch to a secondBWP based on identifying the consistent LBT failures on the first BWP.In some cases, the switching parameter may indicate one or more of: anumber of BWP switches for the UE (e.g., a maximum number of switchesthe UE can perform, a minimum number of switches, fixed number ofswitches, etc.), whether a BWP can be switched to after a failure ofanother BWP, a priority order for BWPs to be switched to, a subbandconstraint for switching BWPs, whether a same BWP can be switched tomultiple times, a maximum time between switching to the same BWP, or acombination thereof.

Based on the information indicated in the switching parameter by thebase station, the UE may select or identify the second BWP and attemptto communicate with the base station using the second BWP. For example,the UE may perform a random access procedure (e.g., a random accesschannel (RACH) procedure) with the base station on the second BWP toestablish a connection with the base station for subsequentcommunications. However, if the random access procedure fails or the UEexperiences another consistent LBT failure on the second BWP, the UE maydeclare a radio link failure (RLF), switch to a third BWP, abort therandom access procedure, or a combination thereof. Additionally oralternatively, if the UE identifies a consistent LBT failure on thefirst BWP or on the second BWP or on both, the UE may report anindication of the LBT failure (e.g., via a medium access control (MAC)control element (CE), a dedicated cause value message, a recoveryprocedure message, etc.) based on a type of cell that the LBT failureoccurs upon (e.g., a primary cell (PCell), a secondary cell (SCell), aprimary SCell (PSCell), etc.).

A method of wireless communications at a UE is described. The method mayinclude receiving, from a base station, a BWP switching configurationmessage including a switching parameter; performing a set of LBTprocedures for a first BWP; and switching to a second BWP for uplinkcommunications with the base station based on the switching parameterand a number of failures associated with the set of LBT procedures forthe first BWP.

An apparatus for wireless communications at a UE is described. Theapparatus may include a processor, memory coupled with the processor,and instructions stored in the memory. The instructions may beexecutable by the processor to cause the apparatus to receive, from abase station, a BWP switching configuration message including aswitching parameter; to perform a set of LBT procedures for a first BWP;and to switch to a second BWP for uplink communications with the basestation based on the switching parameter and a number of failuresassociated with the set of LBT procedures for the first BWP.

Another apparatus for wireless communications at a UE is described. Theapparatus may include means for receiving, from a base station, a BWPswitching configuration message including a switching parameter; meansfor performing a set of LBT procedures for a first BWP; and means forswitching to a second BWP for uplink communications with the basestation based on the switching parameter and a number of failuresassociated with the set of LBT procedures for the first BWP.

A non-transitory computer-readable medium storing code for wirelesscommunications at a UE is described. The code may include instructionsexecutable by a processor to receive, from a base station, a BWPswitching configuration message including a switching parameter; toperform a set of LBT procedures for a first BWP; and to switch to asecond BWP for uplink communications with the base station based on theswitching parameter and a number of failures associated with the set ofLBT procedures for the first BWP.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a number ofBWP switches based on the switching parameter, where the switch to thesecond BWP is based on the number of BWP switches.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the switching parameter mayinclude an upper threshold number of BWP switches, a lower thresholdnumber of BWP switches, a fixed number of BWP switches, or a combinationthereof.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for selecting the secondBWP based on the switching parameter.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the switching parameter mayinclude an indication of a BWP priority order, where selecting thesecond BWP is based on the BWP priority order.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the switching parameter mayinclude an indication of a subband constraint for the second BWP, whereselecting the second BWP is based on the subband constraint.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the second BWP may be whollyin a second subband different than a first subband of the first BWP, asubset of the second BWP may be in the second subband different than thefirst subband of the first BWP, or a combination thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the switching parameter mayinclude an indication that switching to a same BWP multiple times ispermissible, where selecting the second BWP is based on the indication.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a timethreshold for switching to the same BWP, where selecting the second BWPis based on a time between successive switches to the second BWPsatisfying the time threshold.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for performing a randomaccess procedure on the second BWP based on switching to the second BWP.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting a firstmessage of the random access procedure; determining a threshold numberof attempts for transmitting the first message has been satisfied; anddeclaring an RLF or switching to a third BWP or a combination thereofbased on the threshold number of attempts for transmitting the firstmessage being satisfied.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a number ofuplink LBT failures for the second BWP exceeds the threshold value;switching to a third BWP based on the number of uplink LBT failures forthe second BWP exceeding the threshold value; and aborting the randomaccess procedure on the second BWP.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining that thenumber of uplink LBT failures for the first BWP occur on a PSCell andtransmitting a dedicated cause value for the number of uplink LBTfailures for the first BWP in a secondary cell group (SCG) failuremessage.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the dedicated cause value mayinclude a number of switched BWPs attempted.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining that thenumber of uplink LBT failures for the first BWP occur on an SCell andtransmitting a MAC CE indicating the uplink LBT failures on a PCell oran additional SCell.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the MAC CE mayinclude operations, features, means, or instructions for determining theSCell includes a set of BWPs that includes the first BWP andtransmitting the MAC CE on an additional BWP in a different subband forthe SCell than the first BWP.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining to switchto the second BWP based on the number of failures associated with theset of LBT procedures for the first BWP satisfying a threshold value.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for performing a mastercell group (MCG) recovery procedure via a secondary node (SN) based on adetermination that a number of uplink LBT failures for the second BWPsatisfies the threshold value and that the number of uplink LBT failuresfor the second BWP occurs on a PCell.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, performing the MCG recoveryprocedure via the SN may include operations, features, means, orinstructions for transmitting an indication of a failure for the PCellbased on the number of uplink LBT failures for the second BWP exceedingthe threshold value to the SN.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for performing one or moreLBT procedures for the second BWP and switching to a third BWP accordingto the BWP switching configuration and the switching parameter based ona number of failures associated with the one or more LBT procedures forthe second BWP.

A method of wireless communications at a base station is described. Themethod may include transmitting, to a UE, a BWP switching configurationmessage including a switching parameter; receiving, from the UE, a firstuplink transmission in a first BWP; and receiving, from the UE, anuplink transmission in a second BWP based on the switching parameter andan uplink LBT failure.

An apparatus for wireless communications at a base station is described.The apparatus may include a processor, memory coupled with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to cause the apparatus to transmit, to aUE, a BWP switching configuration message including a switchingparameter; to receive, from the UE, a first uplink transmission in afirst BWP; and to receive, from the UE, an uplink transmission in asecond BWP based on the switching parameter and an uplink LBT failure.

Another apparatus for wireless communications at a base station isdescribed. The apparatus may include means for transmitting, to a UE, aBWP switching configuration message including a switching parameter;means for receiving, from the UE, a first uplink transmission in a firstBWP; and means for receiving, from the UE, an uplink transmission in asecond BWP based on the switching parameter and an uplink LBT failure.

A non-transitory computer-readable medium storing code for wirelesscommunications at a base station is described. The code may includeinstructions executable by a processor to transmit, to a UE, a BWPswitching configuration message including a switching parameter; toreceive, from the UE, a first uplink transmission in a first BWP; and toreceive, from the UE, an uplink transmission in a second BWP based onthe switching parameter and an uplink LBT failure.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving, from the UE,a dedicated cause value for a number of uplink LBT failures for thefirst BWP in an SCG failure message, where the dedicated cause valueincludes a number of switched BWPs attempted.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving, from the UE,a MAC CE indicating a number of uplink LBT failures for the first BWP ona PCell or an SCell.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the MAC CE may be received onan additional BWP in a different subband for the SCell than the firstBWP.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving, from an SN,an indication of a failure for a PCell based on a number of uplink LBTfailures for the first BWP exceeding a threshold value.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the switching parameter mayinclude a number of BWP switches, an indication of which BWP can beswitched to after a failure of another BWP, a priority order for a setof BWPs in the BWP switching configuration message, an indication forswitching to a BWP in a different subband, an indication that a same BWPcan be used multiple times for switching, a threshold time betweenswitching to the same BWP, or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communicationsthat supports uplink listen-before-talk (LBT) failure recovery inaccordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a bandwidth part (BWP) switchingconfiguration that supports uplink LBT failure recovery in accordancewith aspects of the present disclosure.

FIG. 3 illustrates an example of a wireless communications system thatsupports uplink LBT failure recovery in accordance with aspects of thepresent disclosure.

FIG. 4 illustrates an example of a process flow that supports uplink LBTfailure recovery in accordance with aspects of the present disclosure.

FIGS. 5 and 6 show block diagrams of devices that support uplink LBTfailure recovery in accordance with aspects of the present disclosure.

FIG. 7 shows a block diagram of a user equipment (UE) communicationsmanager that supports uplink LBT failure recovery in accordance withaspects of the present disclosure.

FIG. 8 shows a diagram of a system including a device that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure.

FIGS. 9 and 10 show block diagrams of devices that support uplink LBTfailure recovery in accordance with aspects of the present disclosure.

FIG. 11 shows a block diagram of a base station communications managerthat supports uplink LBT failure recovery in accordance with aspects ofthe present disclosure.

FIG. 12 shows a diagram of a system including a device that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure.

FIGS. 13 through 18 show flowcharts illustrating methods that supportuplink LBT failure recovery in accordance with aspects of the presentdisclosure.

DETAILED DESCRIPTION

In some wireless communications systems (e.g., New Radio unlicensed(NR-U) bands), a UE may perform a listen-before-talk (LBT) procedure todetermine if a channel is unoccupied for uplink transmissions and maytransmit an uplink transmission after determining the LBT procedure issuccessful (e.g., the channel is clear). For a dual connectivityconfiguration (e.g., or carrier aggregation configuration), if the UEdetects consistent failures for an LBT procedure on a current uplinkbandwidth part (BWP) (e.g., a number of LBT procedures fail that exceeda configured number of attempts) on a primary cell (PCell) (e.g., or aprimary secondary cell (PSCell)), the UE may switch to another BWP forrecovery. However, some techniques for switching to another BWP may notinclude parameters for the switching. For example, the UE may attempt toswitch to a BWP in a same subband as the failed BWP, may attempt toswitch to a BWP in an adjacent subband as the failed BWP, or may attemptto switch to a same BWP tried earlier and had already previously failed.As such, the UE may inefficiently try different BWPs before finding aclear channel to use for uplink transmissions, which may increaselatency and delay the uplink transmissions unnecessarily.

As described herein, a base station (or the network) may indicatedifferent parameters (e.g., a switching parameter) for the UE to switchbetween different BWPs based on identifying consistent LBT failures fora BWP. For example, the base station may indicate a number of BWPswitches for the UE (e.g., a maximum number of switches the UE canperform, a minimum number of switches, a fixed number of switches,etc.), whether a BWP can be switched to after a failure of another BWP,a priority order for BWPs to be switched to, switching to a BWP in adifferent subband than the failed BWP, whether a same BWP can beswitched to multiple times, a maximum time between switching to the sameBWP, or a combination thereof. Accordingly, based on the informationindicated with the switching parameter(s) from the base station, the UEmay select or identify a second BWP and attempt to communicate with thebase station using the second BWP.

In some cases, the UE may then perform a random access procedure (e.g.,a random access channel (RACH) procedure) on the second BWP (e.g., BWPthat the UE switched to). If a RACH failure occurs on the second BWP,the UE may declare a radio link failure (RLF) or switch to a differentBWP (e.g., a third BWP). Additionally, if the UE identifies a consistentLBT failure on the second BWP, the UE may switch to a different BWP andabort RACH on the second BWP. In some cases, if the consistent LBTfailures occur on a PSCell, the UE may signal a dedicated cause value(e.g., including a number of switched BWPs) in a secondary cell group(SCG) failure message for the PSCell. Additionally or alternatively, ifthe consistent LBT failures occur on a BWP in a secondary cell (SCell)(e.g., for a dual connectivity or carrier aggregation configuration),the UE may transmit a medium access control (MAC) control element (CE)on a PCell, an additional SCell, or on an additional BWP for the SCell.Additionally or alternatively, if the consistent LBT failures occur onthe PCell, the UE may perform a master cell group (MCG) recovery througha secondary node (SN) (e.g., secondary base station) that forwards therecovery to the base station (e.g., master node (MN), PCell, etc.).

Aspects of the disclosure are initially described in the context ofwireless communications systems. Additionally, aspects of the disclosureare illustrated through a BWP switching configuration, an additionalwireless communications system, and a process flow. Aspects of thedisclosure are further illustrated by and described with reference toapparatus diagrams, system diagrams, and flowcharts that relate touplink LBT failure recovery.

FIG. 1 illustrates an example of a wireless communications system 100that supports uplink LBT failure recovery in accordance with aspects ofthe present disclosure. The wireless communications system 100 mayinclude one or more base stations 105, one or more UEs 115, and a corenetwork 130. In some examples, the wireless communications system 100may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A)network, an LTE-A Pro network, or a New Radio (NR) network. In someexamples, the wireless communications system 100 may support enhancedbroadband communications, ultra-reliable (e.g., mission critical)communications, low latency communications, communications with low-costand low-complexity devices, or any combination thereof.

The base stations 105 may be dispersed throughout a geographic area toform the wireless communications system 100 and may be devices indifferent forms or having different capabilities. The base stations 105and the UEs 115 may wirelessly communicate via one or more communicationlinks 125. Each base station 105 may provide a coverage area 110 overwhich the UEs 115 and the base station 105 may establish one or morecommunication links 125. The coverage area 110 may be an example of ageographic area over which a base station 105 and a UE 115 may supportthe communication of signals according to one or more radio accesstechnologies.

The UEs 115 may be dispersed throughout a coverage area 110 of thewireless communications system 100, and each UE 115 may be stationary,or mobile, or both at different times. The UEs 115 may be devices indifferent forms or having different capabilities. Some example UEs 115are illustrated in FIG. 1 . The UEs 115 described herein may be able tocommunicate with various types of devices, such as other UEs 115, thebase stations 105, or network equipment (e.g., core network nodes, relaydevices, integrated access and backhaul (IAB) nodes, or other networkequipment), as shown in FIG. 1 .

The base stations 105 may communicate with the core network 130, or withone another, or both. For example, the base stations 105 may interfacewith the core network 130 through one or more backhaul links 120 (e.g.,via an S1, N2, N3, or other interface). The base stations 105 maycommunicate with one another over the backhaul links 120 (e.g., via anX2, Xn, or other interface) either directly (e.g., directly between basestations 105), or indirectly (e.g., via core network 130), or both. Insome examples, the backhaul links 120 may be or include one or morewireless links.

One or more of the base stations 105 described herein may include or maybe referred to by a person having ordinary skill in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or agiga-NodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or other suitable terminology.

A UE 115 may include or may be referred to as a mobile device, awireless device, a remote device, a handheld device, or a subscriberdevice, or some other suitable terminology, where the “device” may alsobe referred to as a unit, a station, a terminal, or a client, amongother examples. A UE 115 may also include or may be referred to as apersonal electronic device such as a cellular phone, a personal digitalassistant (PDA), a tablet computer, a laptop computer, or a personalcomputer. In some examples, a UE 115 may include or be referred to as awireless local loop (WLL) station, an Internet of Things (IoT) device,an Internet of Everything (IoE) device, or a machine type communications(MTC) device, among other examples, which may be implemented in variousobjects such as appliances, or vehicles, meters, among other examples.

The UEs 115 described herein may be able to communicate with varioustypes of devices, such as other UEs 115 that may sometimes act as relaysas well as the base stations 105 and the network equipment includingmacro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations,among other examples, as shown in FIG. 1 .

The UEs 115 and the base stations 105 may wirelessly communicate withone another via one or more communication links 125 over one or morecarriers. The term “carrier” may refer to a set of radio frequencyspectrum resources having a defined physical layer structure forsupporting the communication links 125. For example, a carrier used fora communication link 125 may include a portion of a radio frequencyspectrum band (e.g., a BWP) that is operated according to one or morephysical layer channels for a given radio access technology (e.g., LTE,LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisitionsignaling (e.g., synchronization signals, system information), controlsignaling that coordinates operation for the carrier, user data, orother signaling. The wireless communications system 100 may supportcommunication with a UE 115 using carrier aggregation or multi-carrieroperation. A UE 115 may be configured with multiple downlink componentcarriers and one or more uplink component carriers according to acarrier aggregation configuration. Carrier aggregation may be used withboth frequency division duplexing (FDD) and time division duplexing(TDD) component carriers.

In some examples (e.g., in a carrier aggregation configuration), acarrier may also have acquisition signaling or control signaling thatcoordinates operations for other carriers. A carrier may be associatedwith a frequency channel (e.g., an evolved universal mobiletelecommunication system terrestrial radio access (E-UTRA) absoluteradio frequency channel number (EARFCN)) and may be positioned accordingto a channel raster for discovery by the UEs 115. A carrier may beoperated in a standalone mode where initial acquisition and connectionmay be conducted by the UEs 115 via the carrier, or the carrier may beoperated in a non-standalone mode where a connection is anchored using adifferent carrier (e.g., of the same or a different radio accesstechnology).

The communication links 125 shown in the wireless communications system100 may include uplink transmissions from a UE 115 to a base station105, or downlink transmissions from a base station 105 to a UE 115.Carriers may carry downlink or uplink communications (e.g., in an FDDmode) or may be configured to carry downlink and uplink communications(e.g., in a TDD mode).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of determined bandwidths for carriers of a particular radioaccess technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz(MHz)). Devices of the wireless communications system 100 (e.g., thebase stations 105, the UEs 115, or both) may have hardwareconfigurations that support communications over a particular carrierbandwidth or may be configurable to support communications over one of aset of carrier bandwidths. In some examples, the wireless communicationssystem 100 may include base stations 105 or UEs 115 that supportsimultaneous communications via carriers associated with multiplecarrier bandwidths. In some examples, each served UE 115 may beconfigured for operating over portions (e.g., a sub-band, a BWP) or allof a carrier bandwidth.

Signal waveforms transmitted over a carrier may be made up of multiplesubcarriers (e.g., using multi-carrier modulation (MCM) techniques suchas orthogonal frequency division multiplexing (OFDM) or discrete Fouriertransform spread OFDM (DFT-S-OFDM)). In a system employing MCMtechniques, a resource element may consist of one symbol period (e.g., aduration of one modulation symbol) and one subcarrier, where the symbolperiod and subcarrier spacing are inversely related. The number of bitscarried by each resource element may depend on the modulation scheme(e.g., the order of the modulation scheme, the coding rate of themodulation scheme, or both). Thus, the more resource elements that a UE115 receives and the higher the order of the modulation scheme, thehigher the data rate may be for the UE 115. A wireless communicationsresource may refer to a combination of a radio frequency spectrumresource, a time resource, and a spatial resource (e.g., spatial layersor beams), and the use of multiple spatial layers may further increasethe data rate or data integrity for communications with a UE 115.

The time intervals for the base stations 105 or the UEs 115 may beexpressed in multiples of a basic time unit which may, for example,refer to a sampling period of T_(s)=1/(Δf_(max)·N_(f)) seconds, whereΔf_(max) may represent the maximum supported subcarrier spacing, andN_(f) may represent the maximum supported discrete Fourier transform(DFT) size. Time intervals of a communications resource may be organizedaccording to radio frames each having a specified duration (e.g., 10milliseconds (ms)). Each radio frame may be identified by a system framenumber (SFN) (e.g., ranging from 0 to 1023).

Each frame may include multiple consecutively numbered subframes orslots, and each subframe or slot may have the same duration. In someexamples, a frame may be divided (e.g., in the time domain) intosubframes, and each subframe may be further divided into a number ofslots. Alternatively, each frame may include a variable number of slots,and the number of slots may depend on subcarrier spacing. Each slot mayinclude a number of symbol periods (e.g., depending on the length of thecyclic prefix prepended to each symbol period). In some wirelesscommunications systems 100, a slot may further be divided into multiplemini-slots containing one or more symbols. Excluding the cyclic prefix,each symbol period may contain one or more (e.g., N_(f)) samplingperiods. The duration of a symbol period may depend on the subcarrierspacing or frequency band of operation.

A subframe, a slot, a mini-slot, or a symbol may be the smallestscheduling unit (e.g., in the time domain) of the wirelesscommunications system 100 and may be referred to as a transmission timeinterval (TTI). In some examples, the TTI duration (e.g., the number ofsymbol periods in a TTI) may be variable. Additionally or alternatively,the smallest scheduling unit of the wireless communications system 100may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using one or more oftime division multiplexing (TDM) techniques, frequency divisionmultiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A controlregion (e.g., a control resource set (CORESET)) for a physical controlchannel may be defined by a number of symbol periods and may extendacross the system bandwidth or a subset of the system bandwidth of thecarrier. One or more control regions (e.g., CORESETs) may be configuredfor a set of the UEs 115. For example, one or more of the UEs 115 maymonitor or search control regions for control information according toone or more search space sets, and each search space set may include oneor multiple control channel candidates in one or more aggregation levelsarranged in a cascaded manner. An aggregation level for a controlchannel candidate may refer to a number of control channel resources(e.g., control channel elements (CCEs)) associated with encodedinformation for a control information format having a given payloadsize. Search space sets may include common search space sets configuredfor sending control information to multiple UEs 115 and UE-specificsearch space sets for sending control information to a specific UE 115.

Each base station 105 may provide communication coverage via one or morecells, for example a macro cell, a small cell, a hot spot, or othertypes of cells, or any combination thereof. The term “cell” may refer toa logical communication entity used for communication with a basestation 105 (e.g., over a carrier) and may be associated with anidentifier for distinguishing neighboring cells (e.g., a physical cellidentifier (PCID), a virtual cell identifier (VCID), or others). In someexamples, a cell may also refer to a geographic coverage area 110 or aportion of a geographic coverage area 110 (e.g., a sector) over whichthe logical communication entity operates. Such cells may range fromsmaller areas (e.g., a structure, a subset of structure) to larger areasdepending on various factors such as the capabilities of the basestation 105. For example, a cell may be or include a building, a subsetof a building, or exterior spaces between or overlapping with geographiccoverage areas 110, among other examples.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by theUEs 115 with service subscriptions with the network provider supportingthe macro cell. A small cell may be associated with a lower-powered basestation 105, as compared with a macro cell, and a small cell may operatein the same or different (e.g., licensed, unlicensed) frequency bands asmacro cells. Small cells may provide unrestricted access to the UEs 115with service subscriptions with the network provider or may providerestricted access to the UEs 115 having an association with the smallcell (e.g., the UEs 115 in a closed subscriber group (CSG), the UEs 115associated with users in a home or office). A base station 105 maysupport one or multiple cells and may also support communications overthe one or more cells using one or multiple component carriers.

In some cases, wireless communications system 100 may utilize bothlicensed and unlicensed radio frequency spectrum bands. For example,wireless communications system 100 may employ License Assisted Access(LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technologyin an unlicensed band such as the 5 GHz ISM band. When operating inunlicensed radio frequency spectrum bands, wireless devices such as basestations 105 and UEs 115 may employ LBT procedures to ensure a frequencychannel is clear before transmitting data. In some cases, operations inunlicensed bands may be based on a carrier aggregation configuration inconjunction with component carriers operating in a licensed band (e.g.,LAA). Operations in unlicensed spectrum may include downlinktransmissions, uplink transmissions, peer-to-peer transmissions, or acombination of these. Duplexing in unlicensed spectrum may be based onFDD, TDD, or a combination of both.

In some examples, a base station 105 may be movable and thereforeprovide communication coverage for a moving geographic coverage area110. In some examples, different geographic coverage areas 110associated with different technologies may overlap, but the differentgeographic coverage areas 110 may be supported by the same base station105. In other examples, the overlapping geographic coverage areas 110associated with different technologies may be supported by differentbase stations 105. The wireless communications system 100 may include,for example, a heterogeneous network in which different types of thebase stations 105 provide coverage for various geographic coverage areas110 using the same or different radio access technologies.

The wireless communications system 100 may be configured to supportultra-reliable communications or low-latency communications, or variouscombinations thereof. For example, the wireless communications system100 may be configured to support ultra-reliable low-latencycommunications (URLLC) or mission critical communications. The UEs 115may be designed to support ultra-reliable, low-latency, or criticalfunctions (e.g., mission critical functions). Ultra-reliablecommunications may include private communication or group communicationand may be supported by one or more mission critical services such asmission critical push-to-talk (MCPTT), mission critical video (MCVideo),or mission critical data (MCData). Support for mission criticalfunctions may include prioritization of services, and mission criticalservices may be used for public safety or general commercialapplications. The terms ultra-reliable, low-latency, mission critical,and ultra-reliable low-latency may be used interchangeably herein.

In some examples, a UE 115 may also be able to communicate directly withother UEs 115 over a device-to-device (D2D) communication link 135(e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs 115utilizing D2D communications may be within the geographic coverage area110 of a base station 105. Other UEs 115 in such a group may be outsidethe geographic coverage area 110 of a base station 105 or be otherwiseunable to receive transmissions from a base station 105. In someexamples, groups of the UEs 115 communicating via D2D communications mayutilize a one-to-many (1:M) system in which each UE 115 transmits toevery other UE 115 in the group. In some examples, a base station 105facilitates the scheduling of resources for D2D communications. In othercases, D2D communications are carried out between the UEs 115 withoutthe involvement of a base station 105.

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC) or 5G core (5GC), which may include at leastone control plane entity that manages access and mobility (e.g., amobility management entity (MME), an access and mobility managementfunction (AMF)) and at least one user plane entity that routes packetsor interconnects to external networks (e.g., a serving gateway (S-GW), aPacket Data Network (PDN) gateway (P-GW), or a user plane function(UPF)). The control plane entity may manage non-access stratum (NAS)functions such as mobility, authentication, and bearer management forthe UEs 115 served by the base stations 105 associated with the corenetwork 130. User IP packets may be transferred through the user planeentity, which may provide IP address allocation as well as otherfunctions. The user plane entity may be connected to the networkoperators IP services 150. The operators IP services 150 may includeaccess to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS),or a Packet-Switched Streaming Service.

Some of the network devices, such as a base station 105, may includesubcomponents such as an access network entity 140, which may be anexample of an access node controller (ANC). Each access network entity140 may communicate with the UEs 115 through one or more other accessnetwork transmission entities 145, which may be referred to as radioheads, smart radio heads, or transmission/reception points (TRPs). Eachaccess network transmission entity 145 may include one or more antennapanels. In some configurations, various functions of each access networkentity 140 or base station 105 may be distributed across various networkdevices (e.g., radio heads and ANCs) or consolidated into a singlenetwork device (e.g., a base station 105).

The wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 megahertz (MHz) to 300gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known asthe ultra-high frequency (UHF) region or decimeter band because thewavelengths range from approximately one decimeter to one meter inlength. The UHF waves may be blocked or redirected by buildings andenvironmental features, but the waves may penetrate structuressufficiently for a macro cell to provide service to the UEs 115 locatedindoors. The transmission of UHF waves may be associated with smallerantennas and shorter ranges (e.g., less than 100 kilometers) compared totransmission using the smaller frequencies and longer waves of the highfrequency (HF) or very high frequency (VHF) portion of the spectrumbelow 300 MHz.

The wireless communications system 100 may utilize both licensed andunlicensed radio frequency spectrum bands. For example, the wirelesscommunications system 100 may employ License Assisted Access (LAA),LTE-Unlicensed (LTE-U) radio access technology, or NR technology in anunlicensed band such as the 5 GHz industrial, scientific, and medical(ISM) band. When operating in unlicensed radio frequency spectrum bands,devices such as the base stations 105 and the UEs 115 may employ carriersensing for collision detection and avoidance. In some examples,operations in unlicensed bands may be based on a carrier aggregationconfiguration in conjunction with component carriers operating in alicensed band (e.g., LAA). Operations in unlicensed spectrum may includedownlink transmissions, uplink transmissions, P2P transmissions, or D2Dtransmissions, among other examples.

A base station 105 or a UE 115 may be equipped with multiple antennas,which may be used to employ techniques such as transmit diversity,receive diversity, multiple-input multiple-output (MIMO) communications,or beamforming. The antennas of a base station 105 or a UE 115 may belocated within one or more antenna arrays or antenna panels, which maysupport MIMO operations or transmit or receive beamforming. For example,one or more base station antennas or antenna arrays may be co-located atan antenna assembly, such as an antenna tower. In some examples,antennas or antenna arrays associated with a base station 105 may belocated in diverse geographic locations. A base station 105 may have anantenna array with a number of rows and columns of antenna ports thatthe base station 105 may use to support beamforming of communicationswith a UE 115. Likewise, a UE 115 may have one or more antenna arraysthat may support various MIMO or beamforming operations. Additionally oralternatively, an antenna panel may support radio frequency beamformingfor a signal transmitted via an antenna port.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105, a UE 115) to shape or steeran antenna beam (e.g., a transmit beam, a receive beam) along a spatialpath between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that some signals propagatingat particular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying amplitude offsets, phase offsets, or both to signals carriedvia the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

The wireless communications system 100 may be a packet-based networkthat operates according to a layered protocol stack. In the user plane,communications at the bearer or Packet Data Convergence Protocol (PDCP)layer may be IP-based. A Radio Link Control (RLC) layer may performpacket segmentation and reassembly to communicate over logical channels.A MAC layer may perform priority handling and multiplexing of logicalchannels into transport channels. The MAC layer may also use errordetection techniques, error correction techniques, or both to supportretransmissions at the MAC layer to improve link efficiency. In thecontrol plane, the Radio Resource Control (RRC) protocol layer mayprovide establishment, configuration, and maintenance of an RRCconnection between a UE 115 and a base station 105 or a core network 130supporting radio bearers for user plane data. At the physical layer,transport channels may be mapped to physical channels.

In some wireless communications systems, a UE 115 may support carrieraggregation or dual connectivity or both, where the UE 115 communicateswith multiple cells simultaneously. For example, the UE may communicatewith a first base station 105 (e.g., a PCell)) and with a second basestation 105 (e.g., an SCell) at the same time. Additionally oralternatively, a single base station 105 may include multiple cells(e.g., both a PCell and an SCell), where the UE 115 communicates withtwo or more cells on the single base station 105 at the same time. Insome cases, one or more of the cells may be grouped into a PCell group(e.g., an MCG), which may include the PCell and one or more SCells.Additionally, one or more SCells may be grouped into an SCell group(e.g., an SCG). In some cases, a PSCell may be configured for the one ormore SCells. Communications on each cell group may be independent ofeach other.

For communications between a UE 115 and a base station 105, an availablebandwidth of frequencies for the communications may be split into BWPsthat are subsets of the available bandwidth of frequencies. A BWP may bea bandwidth where the UE 115 can transmit and receive information. Inconventional systems, a maximum number of four (4) BWPs may beconfigured to the UE 115. In some cases, the UE 115 may monitor asingle, active BWP at a time (e.g., on a PCell). Additionally, on anSCell, the UE 115 may have multiple active BWPs at a given time.

In some cases, a carrier may be split into the one or more BWPs based onthe size of the carrier exceeding a bandwidth threshold (e.g., greaterthan 20 MHz). Each of the BWPs may further include one or moresub-channels (e.g., subbands), where each sub-channel is a samebandwidth (e.g., 20 MHz). Accordingly, each BWP may vary in size (e.g.,in multiples of 20 MHz) based on the number of sub-channels located ineach. The BWPs and corresponding sub-channels may be part of a sharedradio frequency (RF) spectrum (e.g., an unlicensed or shared licensedspectrum, such as NR-U) for which one or more wireless devices (e.g.,base stations 105 and UEs 115) contend. A wireless device (for example,a base station 105, a UE 115, etc.) may determine which sub-channels areavailable for communications with other wireless devices based on an LBTprocedure that indicates if on-going communications are present on eachof the sub-channels.

For example, prior to transmitting the one or more uplink signals, a UE115 may perform an LBT (e.g., an LBT procedure, a clear channelassessment (CCA), etc.) based on communicating with base station 105 inan unlicensed band (e.g., unlicensed frequency band, NR-U, etc.). Insome cases, the LBT may include the UE 115 listening to uplink resources(e.g., indicated by an uplink grant from the base station 105) fortransmitting one or more uplink signals to determine whether the channelis clear before attempting to transmit on the uplink resources.Accordingly, if the UE 115 detects a signal (e.g., above a thresholdpower value, for example) on the uplink resources during the LBT, the UE115 may refrain from transmitting the uplink signals. Alternatively, ifthe UE 115 does not detect a signal, the UE 115 may determine the LBT issuccessful and may proceed with transmitting the uplink signals.

Accordingly, in some wireless communications system (e.g., NR-U), the UE115 may perform an LBT for uplink transmissions and may transmit theuplink transmissions after LBT is successful. In some cases, a detectionand recovery mechanism may be used by the UE 115 when consistent uplinkLBT failures happen. The consistent uplink LBT failure may be considereda triggering event for the UE 115 based on a number of consecutive LBTfailures occurring in a row (e.g., a configurable number of consecutiveLBT failures indicated to the UE 115, such as by a base station 105 viaRRC signaling, or preconfigured in the UE 115). For example, for aprimary cell (e.g., PCell or PSCell), if the UE 115 detects consistentLBT failures on an existing uplink BWP being monitored or intended to beused by the UE 115, the UE 115 may switch to another BWP for recovery.

As part of this detection and recovery mechanism, the MAC layer (e.g.,and additional upper layers) may rely on reception of a notification ofan uplink LBT failure from the physical layer to detect a consistentuplink LBT failure. Subsequently, the UE 115 may switch to another BWPand may initiate a RACH procedure (e.g., random access procedure) upondeclaration of the consistent LBT failure on a PCell or a PSCell ifthere is another BWP with configured RACH resources (e.g., physical RACH(PRACH) resources). In some cases, the UE shall perform an RLF recoveryif the consistent uplink LBT failure was detected on the PCell and anuplink LBT failure was detected on N possible BWPs. Additionally oralternatively, when consistent uplink LBT failures are detected on thePSCell, the UE 115 may inform a MN (e.g., base station 105) of theconsistent uplink LBT failures via an SCG failure information procedureafter detecting the consistent uplink LBT failures on N BWPs.

In some cases, N may represent a number of configured BWPs withconfigured PRACH resources for the UE 115 to use. For example, N may beindicated to the UE 115 by a base station 105 (e.g., MN, scheduling basestation 105, etc.). If N is larger than one (1), the UE 115 may select anext BWP for switching based on UE implementation. Additionally, whenconsistent uplink LBT failures are detected on an SCell, the UE 115 maytransmit a MAC CE to report the consistent uplink LBT failures to a nodewhere the SCell belongs (e.g., secondary base station, SN, etc.).

However, with the detection and recovery mechanism as describedpreviously, no parameters are indicated to the UE 115 for the BWPswitching, and determining which BWP to switch to is left up to the UE115. For example, the UE 115 may attempt to switch to a BWP in a samesubband as the failed BWP, may attempt to switch to a BWP in an adjacentsubband as the failed BWP, or may attempt to switch to a same BWP triedearlier and had already previously failed. As such, the UE mayinefficiently try different BWPs with a higher chance of also failingbefore finding a clear channel to use for uplink transmissions, whichmay increase latency and delay the uplink transmissions unnecessarily.

Wireless communications system 100 may include efficient techniques fora UE 115 to identify a BWP to switch to after identifying consistentuplink LBT failures on a first BWP based on parameters indicated by abase station 105. For example, the base station 105 may transmit aswitching parameter to the UE 115 that the UE 115 then uses to switch toa second BWP based on identifying the consistent uplink LBT failures onthe first BWP. In some cases, the switching parameter may include anumber of BWP switches for the UE 115 (e.g., a maximum number ofswitches the UE 115 can perform, a minimum number of switches, fixednumber of switches, etc.), whether a BWP can be switched to after afailure of another BWP, a priority order for BWPs to be switched to,switching to a BWP in a different subband than the failed BWP, whether asame BWP can be switched to multiple times, a maximum time betweenswitching to the same BWP, or a combination thereof. Subsequently, afterselecting the second BWP, the UE 115 may attempt to use the second BWPfor sending uplink transmissions to the base station 105 (e.g., afterperforming a RACH procedure). Additionally, the UE 115 may transmit anindication of the consistent uplink LBT failures to a base station 105associated with the failed BWP based on a type of cell that is usingthat failed BWP.

FIG. 2 illustrates an example of a BWP switching configuration 200 thatsupports uplink LBT failure recovery in accordance with aspects of thepresent disclosure. In some examples, BWP switching configuration 200may implement aspects of wireless communications system 100. Forexample, BWP switching configuration 200 may include a base station105-a and a UE 115-a, which may be examples of corresponding basestations 105 and UEs 115, respectively, as described with reference toFIG. 1 . In some cases, base station 105-a and UE 115-a may communicateon resources of a carrier 205. Additionally, carrier 205 may includeresources in an unlicensed band (e.g., NR-U communications), and theresources may be divided into one or more BWPs 220 as described herein.

In some cases, based on communicating in the unlicensed band, UE 115-amay perform an LBT 210 in an initial attempt to determine whetherresources are available in a first BWP 220-a of carrier 205 prior totransmitting uplink messages to base station 105-a. However, theresources may be occupied and may be used by another UE 115, a basestation 105, or an additional wireless device. For example, UE 115-a maydetermine a consistent uplink LBT failure is occurring on first BWP220-a based on a number of consecutive LBT failures satisfy a thresholdvalue. In some cases, this threshold value for the number of consecutiveLBT failures to be considered a consistent uplink LBT failure may beconfigurable and indicated to UE 115-a by base station 105-a (e.g., viaRRC signaling) or may be preconfigured in UE 115-a. Accordingly, afteridentifying the consistent LBT failure on first BWP 220-a, UE 115-a mayswitch to a different BWP 220 and attempt a subsequent LBT 225 on thisdifferent BWP 220.

Rather than leaving the determination up to UE implementation fordetermining which BWP 220 to switch to, base station 105-a may transmita switching parameter 215 to UE 115-a. UE 115-a may then use informationincluded in switching parameter 215 to perform a BWP switch 230 and fordetermining a next BWP 220 to switch to and attempt to communicate withbase station 105-a. In some cases, the number of BWPs 220 available forUE 115-a to switch to (N) may be indicated to UE 115-a by base station105-a. As described herein, N may represent a number of configured BWPs220 with configured PRACH resources for the UE 115 to use. While five(5) BWPs 220 are shown in FIG. 2 (e.g., N=5 with first BWP 220-a, asecond BWP 220-b, a third BWP 220-c, a fourth BWP 220-d, and a fifth BWP220-e), the number of BWPs 220 may be higher or lower than five (5).Additionally, while the five (5) BWPs 220 are shown to be consecutive inthe frequency domain (e.g., each BWP 220 appears to abut another BWP220), it is to be understood that the BWPs 220 may be spread out amongthe resources of the unlicensed band of carrier 205.

In some cases, switching parameter 215 may indicate a configured numberof BWP switches 230 for UE 115-a. For example, the number of BWPswitches 230 may represent a maximum number (e.g., upper threshold) ofBWP switches 230 that UE 115-a can perform (e.g., before determining anRLF), a minimum number (e.g., lower threshold) of BWP switches 230 forUE 115-a to perform, or a fixed number of BWP switches 230 for UE 115-a.If the number of BWP switched 230 is not included in switching parameter215 (e.g., not configured), UE 115-a may determine a number of BWPswitches 230 to perform and that can be performed autonomously. As shownin the example of FIG. 2 , the number of BWP switches 230 may be three(3) (e.g., a first BWP switch 230-a, a second BWP switch 230-b, and athird BWP switch 230-c).

Additionally or alternatively, switching parameter 215 may indicatewhether a BWP 220 can be switched to after a consistent uplink LBTfailure is identified on another BWP 220. For example, switchingparameter 215 may indicate that UE 115-a can use third BWP 220-c after aconsistent uplink LBT failure is identified on first BWP 220-a.Additionally or alternatively, switching parameter 215 may indicatemultiple BWPs 220 that UE 115-a can use after a consistent uplink LBTfailure is identified on first BWP 220-a, and UE 115-a then may chooseone of the multiple BWPs 220 to use (e.g., based on additionalinformation included in switching parameter 215, based on UEimplementation, etc.). For example, switching parameter 215 may indicatethat UE 115-a can use third BWP 220-c, fourth BWP 220-d, or fifth BWP220-e after a consistent uplink LBT failure is identified on first BWP220-a, and UE 115-a may select fourth BWP 220-d to use as part of firstBWP switch 230-a.

In some cases, switching parameter 215 may indicate one or more BWPs 220that UE 115-a cannot use after consistent uplink LBT failure isidentified on another BWP 220, and UE 115-a may determine to switch to aBWP 220 not indicated. Additionally or alternatively, switchingparameter 215 may indicate, for each of the N BWPs 220, whether each BWP220 can be switched to after a failure of the other BWPs 220. In somecases, switching parameter 215 may include a configuration of a priorityorder to use for each BWP 220. Accordingly, UE 115-a may switch to a BWP220 based on which BWP 220 has a highest priority.

Additionally or alternatively, switching parameter 215 may include anindication of a subband constraint for a BWP switch 230. For example,the indication may include a constraint that a BWP 220 selected for aBWP switch 230 is to be in a different subband than the BWP 220 wherethe consistent uplink LBT failure was identified. For example, afteridentifying the consistent uplink LBT failure in first BWP 220-a that ispart of a first subband, UE 115-a may select a BWP 220 for a BWP switch230 that is in a subband different than the first subband of which firstBWP 220-a is a part. In some cases, the subband constraint may indicatefor UE 115-a to start with a farthest subband away from the firstsubband (e.g., UE 115-a may select fifth BWP 220-e for first BWP switch230-a based on fifth BWP 220-e being in a subband farthest away from asubband of first BWP 220-a). Additionally, either the whole BWP 220 usedfor the BWP switch 230 or a subset of the BWP 220 used for the BWPswitch 230 may be in a different subband than the subband(s) of firstBWP 220-a where the consistent uplink BWP failure happened.

Additionally or alternatively, switching parameter 215 may include aconfiguration of whether a BWP 220 or a particular BWP 220 can beswitched multiple times (e.g., an indication that switching to a sameBWP 220 multiple times is permissible). For example, after performingfirst BWP switch 230-a, UE 115-a may attempt to access first BWP 220-aagain in a subsequent BWP switch (e.g., second BWP switch 230-b, thirdBWP switch 230-c, etc.) based on an indication that first BWP 220-a canbe switched to multiple times. Additionally or alternatively, UE 115-amay refrain from switching to a BWP 220 that has already been switchedto or monitored previously based on this indication. In some cases,switching parameter 215 may further include a configuration of a maximumtime (e.g., time threshold) between switching to a same BWP. Forexample, UE 115-a may select a BWP 220 for a BWP switch 230 based on atime between successive switches to that BWP 220 satisfying the timethreshold. That is, the time threshold may represent a time that UE115-a must wait before attempting to switch to a same BWP 220 againafter a previous attempt to switch to that same BWP 220 wasunsuccessful.

As shown, after performing a BWP switch 230, UE 115-a may perform an LBT225 on the selected (e.g., switched) BWP 220 to determine whether theselected BWP 220 is available for subsequent communications with basestation 105-a. If the LBT 225 is unsuccessful on the selected BWP 220,UE 115-a may perform a subsequent BWP switch 230 (e.g., based on thenumber of BWP switches 230 included in switching parameter 215 ordetermined by UE 115-a). In addition to or rather than performing theLBT 225 on the selected BWP 220, UE 115-a may attempt to access theselected BWP 220 to communicate with base station 105-a (e.g., via arandom access or RACH procedure).

FIG. 3 illustrates an example of a wireless communications system 300that supports uplink LBT failure recovery in accordance with aspects ofthe present disclosure. In some examples, wireless communications system300 may implement aspects of wireless communications systems 100 and BWPswitching configuration 200. For example, wireless communications system300 may include a base station 105-b and a UE 115-b, which may beexamples of corresponding base stations 105 and UEs 115, respectively,as described with reference to FIGS. 1 and 2 . In some cases, basestation 105-b and UE 115-b may communicate on resources of a carrier305. Additionally, carrier 305 may include resources in an unlicensedband (e.g., NR-U communications), and the resources may be divided intoone or more BWPs as described with reference to FIGS. 1 and 2 .

Additionally, as described with reference to FIG. 2 , base station 105-bmay transmit a switching parameter 310 to UE 115-b for UE 115-b todetermine and select a BWP for switching to based on identifying aconsistent uplink LBT failure on a first BWP. For example, UE 115-b mayperform one or more LBT procedure(s) 315 on the first BWP and determinethat the first BWP is unavailable based on an identified consistentuplink LBT failure (e.g., a number of failures associated with the setof LBT procedures 315 for the first BWP satisfies a threshold value).Accordingly, UE 115-b may then perform one or more BWP switches 320based on the information in switching parameter 310 to select a new BWP(e.g., switched BWP) for attempting to connect with base station 105-b.

In some cases, UE 115-b may perform a RACH procedure 325 (e.g., randomaccess procedure) on the new BWP if the failed BWP is within or on aPCell or a PSCell (e.g., of a dual connectivity or carrier aggregationconfiguration). For example, the RACH procedure 325 may include UE 115-btransmitting a RACH preamble (e.g., a message 1 (Msg1) in a four-stepRACH or random access procedure) to base station 105-b. In some cases,the RACH preamble may be randomly selected from a set of 64predetermined sequences. This random selection may enable base station105-b to distinguish between multiple UEs 115 trying to access thesystem simultaneously. Base station 105-b may respond with a randomaccess response (RAR) (e.g., a second message (Msg2)) that provides anuplink resource grant, a timing advance, and a temporary cell radionetwork temporary identifier (C-RNTI). UE 115-b may then transmit an RRCconnection request (e.g., a third message (Msg3)) along with a temporarymobile subscriber identity (TMSI) (if the UE 115 has previously beenconnected to the same wireless network) or a random identifier. The RRCconnection request may also indicate the reason UE 115-b is connectingto the network (e.g., emergency, signaling, data exchange, etc.). Basestation 105-b may respond to the connection request with a contentionresolution message (e.g., a fourth message (Msg4)) addressed to UE115-b, which may provide a new C-RNTI. If UE 115-b receives a contentionresolution message with the correct identification, UE 115-b may proceedwith RRC setup. If UE 115-b does not receive a contention resolutionmessage (e.g., if there is a conflict with another UE 115), UE 115-b mayrepeat the RACH procedure by transmitting a new RACH preamble (e.g., ona different BWP). Such exchange of messages between UE 115-b and basestation 105-b for random access may be referred to as a four-step randomaccess procedure or a four-step RACH procedure.

In other examples, a two-step random access procedure or a two-step RACHprocedure may be performed for random access. For instance, wirelessdevices operating in licensed or unlicensed spectrum within wirelesscommunications system 300 may initiate a two-step RACH procedure toreduce delay in establishing communication with base station 105-b(e.g., as compared to a four-step RACH procedure). In some cases, thetwo-step RACH procedure may operate regardless of whether a wirelessdevice (e.g., UE 115-b) has a valid timing advance (TA). For example, UE115-b may use a valid TA to coordinate the timing of its transmissionsto base station 105-b (e.g., to account for propagation delay) and mayreceive the valid TA as part of the two-step RACH procedure.Additionally, the two-step RACH procedure may be applicable to any cellsize, may work regardless of whether the RACH procedure iscontention-based or contention-free, and may combine multiple RACHmessages from a four-step RACH procedure. For example, the two-step RACHprocedure may include a first message (e.g., a message A (MsgA)) thatcombines the Msg1 and Msg3 of the four-step RACH procedure and a secondmessage (e.g., a message B (MsgB), a success RAR, etc.) that combinesthe Msg2 and Msg4 of the four-step RACH procedure.

However, in some cases, if a RACH failure occurs due to a maximum numberof Msg1 or MsgA attempts (e.g., a threshold number of attempts fortransmitting the first message) when UE 115-b attempts to perform a BWPswitch 320, UE 115-b may declare RLF, or UE 115-b may switch to anotherBWP. Additionally or alternatively, if a consistent uplink LBT failureis identified before a RACH failure, UE 115-b may switch to another BWPand abort the RACH procedure.

Additionally or alternatively, UE 115-b may transmit an LBT failureindication 330 to base station 105-b to indicate a consistent LBT uplinkfailure on a BWP. For example, when the consistent uplink LBT failureoccurs on a PSCell, the LBT failure indication 330 may include adedicated cause value for this event (e.g., the consistent uplink LBTfailure) in an SCG failure message (e.g., rather than an indication of aRACH failure). In some cases, the dedicated cause value may includenumber of switched BWPs that UE 115-b used. Additionally oralternatively, when the consistent uplink LBT failure occurs on a BWPwithin an SCell, the LBT failure indication 330 may include a MAC CE forthis indication on a PCell or another SCell. In some cases, if multipleactive BWPs are within the SCell where the consistent uplink LBT failureoccurs, the LBT failure indication 330 may include an indication on adifferent BWP in this SCell in a different sub-band. Additionally oralternatively, when the consistent uplink LBT failure occurs on a PCell(e.g., after all the BWP switching and attempts on these) for a dualconnectivity configuration (e.g., or carrier aggregation configuration),UE 115-b may perform a MCG recovery through a SN (e.g., secondary basestation 105), and the LBT failure indication 330 may include anindication of the consistent uplink LBT failure that UE 115-b transmitsto the SN which then forwards the LBT failure indication 330 to basestation 105-b (e.g., MN).

FIG. 4 illustrates an example of a process flow 400 that supports uplinkLBT failure recovery in accordance with aspects of the presentdisclosure. In some examples, process flow 400 may implement aspects ofwireless communications systems 100, BWP switching configuration 200,and wireless communications systems 300. For example, process flow 400may include a base station 105-c and a UE 115-c, which may be examplesof corresponding base stations 105 and UEs 115, respectively, asdescribed with reference to FIGS. 1-3 .

In the following description of the process flow 400, the operationsbetween UE 115-c and base station 105-c may be performed in differentorders or at different times. Certain operations may also be left out ofthe process flow 400, or other operations may be added to the processflow 400. It is to be understood that while UE 115-c and base station105-c are shown performing a number of the operations of the processflow 400, any wireless device may perform the operations shown.

At 405, UE 115-c may receive, from base station 105-c, a BWP switchingconfiguration message including a switching parameter. In some cases,the switching parameter may include a number of BWP switches, anindication of which BWP can be switched to after a failure of anotherBWP, a priority order for a plurality of BWPs in the BWP switchingconfiguration message, an indication for switching to a BWP in adifferent subband, an indication that a same BWP can be used multipletimes for switching, a threshold time between switching to the same BWP,or a combination thereof. Additionally or alternatively, the switchingparameter may include an indication of one or more of an upper thresholdnumber of BWP switches, a lower threshold number of BWP switches, afixed number of BWP switches, or a combination thereof.

At 410, UE 115-c may perform a set of LBT procedures for a first BWP.

At 415, UE 115-c may select a second BWP based on the switchingparameter. In some cases, the switching parameter may include anindication of a BWP priority order, where selecting the second BWP isbased on the BWP priority order. Additionally or alternatively, theswitching parameter may include an indication of a subband constraintfor the second BWP, where selecting the second BWP is based on thesubband constraint. In some cases, the second BWP may be wholly in asecond subband different than a first subband of the first BWP, a subsetof the second BWP may be in the second subband different than the firstsubband of the first BWP, or a combination thereof.

In some cases, UE 115-c may determine a number of BWP switches based onthe switching parameter, where the switch to the second BWP is based onthe number of BWP switches. Additionally or alternatively, the switchingparameter may include an indication that switching to a same BWPmultiple times is permissible (e.g., an indication that a same BWP canbe used multiple times for switching), where selecting the second BWP isbased on the indication. In some cases, UE 115-c may determine a timethreshold for switching to the same BWP, where selecting the second BWPis based on a time between successive switches to the second BWPsatisfying the time threshold.

At 420, UE 115-c may switch to the second BWP for uplink communicationswith base station 105-c based on the switching parameter and a number offailures associated with the set of LBT procedures for the first BWP. Insome cases, UE 115-c may determine to switch to the second BWP based onthe number of failures associated with the set of LBT procedures for thefirst BWP satisfying a threshold value.

Additionally, in some cases, UE 115-c may perform one or more LBTprocedures for the second BWP and may switch to a third BWP according tothe BWP switching configuration and the switching parameter based on anumber of failures associated with the one or more LBT procedures forthe second BWP (e.g., satisfying the threshold value).

At 425, UE 115-c may perform a random access procedure (e.g., RACHprocedure) on the second BWP based on switching to the second BWP. Forexample, UE 115-c may transmit a first message (e.g., Msg1, MsgA, etc.)of the random access procedure. In some cases, UE 115-c may determine athreshold number of attempts for transmitting the first message has beensatisfied and may declare an RLF or may switch to a third BWP or acombination thereof based on the threshold number of attempts fortransmitting the first message has been satisfied. Additionally oralternatively, UE 115-c may determine a number of uplink LBT failuresfor the second BWP exceeds the threshold value, may switch to a thirdBWP based on the number of uplink LBT failures for the second BWPexceeding the threshold value, and may abort the random access procedureon the second BWP.

At 430, UE 115-c may determine that the number of uplink LBT failuresfor the first BWP occur on a PSCell and may transmit a dedicated causevalue for the number of uplink LBT failures for the first BWP in an SCGfailure message. In some cases, the dedicated cause value may include anumber of switched BWPs attempted. Additionally or alternatively, UE115-c may determine that the number of uplink LBT failures for the firstBWP occur on an SCell and may transmit a MAC CE indicating the uplinkLBT failures on a PCell or an additional SCell. In some cases, UE 115-cmay determine the SCell includes a set of BWPs that includes the firstBWP and may transmit the MAC CE on an additional BWP in a differentsubband for the SCell than the first BWP.

Additionally or alternatively, UE 115-c may perform an MCG recoveryprocedure via an SN based on a determination that a number of uplink LBTfailures for the second BWP satisfies the threshold value and that thenumber of uplink LBT failures for the second BWP occurs on a PCell. Insome cases, UE 115-c may transmit an indication of a failure for thePCell based on the number of uplink LBT failures for the second BWPexceeding the threshold value to the SN.

At 435, base station 105-c may receive, from UE 115-c, a first uplinktransmission in the first BWP. Additionally or alternatively, basestation 105-c may receive, from UE 115-c, an uplink transmission in thesecond BWP based on the switching parameter and an uplink LBT failure.

FIG. 5 shows a block diagram 500 of a device 505 that supports uplinkLBT failure recovery in accordance with aspects of the presentdisclosure. The device 505 may be an example of aspects of a UE 115 asdescribed herein. The device 505 may include a receiver 510, a UEcommunications manager 515, and a transmitter 520. The device 505 mayalso include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

The receiver 510 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to uplink LBTfailure recovery, etc.). Information may be passed on to othercomponents of the device 505. The receiver 510 may be an example ofaspects of the transceiver 820 described with reference to FIG. 8 . Thereceiver 510 may utilize a single antenna or a set of antennas.

The UE communications manager 515 may receive, from a base station, aBWP switching configuration message including a switching parameter.Additionally, the UE communications manager 515 may perform a set of LBTprocedures for a first BWP. In some cases, the UE communications manager515 may switch to a second BWP for uplink communications with the basestation based on the switching parameter and a number of failuresassociated with the set of LBT procedures for the first BWP. The UEcommunications manager 515 may be an example of aspects of the UEcommunications manager 810 described herein.

Based on the actions performed by the UE communications manager 515, aUE 115 may efficiently identify a BWP to switch to when a first BWP hasa consistent uplink BWP failure occur. Accordingly, the UE 115 may savepower by not having to attempt to use BWPs that are not ideal forswitching. Additionally, the UE 115 may reduce latency associated withtrying and failing with other BWPs that are not ideal for switching.

The UE communications manager 515, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the UE communications manager 515, orits sub-components may be executed by a general-purpose processor, adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), a field-programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The UE communications manager 515, or its sub-components, may bephysically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, the UEcommunications manager 515, or its sub-components, may be a separate anddistinct component in accordance with various aspects of the presentdisclosure. In some examples, the UE communications manager 515, or itssub-components, may be combined with one or more other hardwarecomponents, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

The transmitter 520 may transmit signals generated by other componentsof the device 505. In some examples, the transmitter 520 may becollocated with a receiver 510 in a transceiver module. For example, thetransmitter 520 may be an example of aspects of the transceiver 820described with reference to FIG. 8 . The transmitter 520 may utilize asingle antenna or a set of antennas.

FIG. 6 shows a block diagram 600 of a device 605 that supports uplinkLBT failure recovery in accordance with aspects of the presentdisclosure. The device 605 may be an example of aspects of a device 505,or a UE 115 as described herein. The device 605 may include a receiver610, a UE communications manager 615, and a transmitter 635. The device605 may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

The receiver 610 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to uplink LBTfailure recovery, etc.). Information may be passed on to othercomponents of the device 605. The receiver 610 may be an example ofaspects of the transceiver 820 described with reference to FIG. 8 . Thereceiver 610 may utilize a single antenna or a set of antennas.

The UE communications manager 615 may be an example of aspects of the UEcommunications manager 515 as described herein. The UE communicationsmanager 615 may include a switching parameter receiver 620, an LBTprocedure component 625, and a BWP switching component 630. The UEcommunications manager 615 may be an example of aspects of the UEcommunications manager 810 described herein.

The switching parameter receiver 620 may receive, from a base station, aBWP switching configuration message including a switching parameter.

The LBT procedure component 625 may perform a set of LBT procedures fora first BWP.

The BWP switching component 630 may switch to a second BWP for uplinkcommunications with the base station based on the switching parameterand a number of failures associated with the set of LBT procedures forthe first BWP.

Based on receiving the switching parameter, a processor of a UE 115(e.g., controlling the receiver 610, the transmitter 635, or atransceiver 820 as described with reference to FIG. 8 ) may identify aBWP that has a higher chance of being successful for switching to afteridentifying a consistent uplink LBT failure at a first BWP. Accordingly,the processor may have reduced computational complexity in thatinformation included in the switching parameter is used for identifyingand selecting the BWP to switch to rather than having to determine a BWPto switch to on its own.

The transmitter 635 may transmit signals generated by other componentsof the device 605. In some examples, the transmitter 635 may becollocated with a receiver 610 in a transceiver module. For example, thetransmitter 635 may be an example of aspects of the transceiver 820described with reference to FIG. 8 . The transmitter 635 may utilize asingle antenna or a set of antennas.

FIG. 7 shows a block diagram 700 of a UE communications manager 705 thatsupports uplink LBT failure recovery in accordance with aspects of thepresent disclosure. The UE communications manager 705 may be an exampleof aspects of a UE communications manager 515, a UE communicationsmanager 615, or a UE communications manager 810 described herein. The UEcommunications manager 705 may include a switching parameter receiver710, an LBT procedure component 715, a BWP switching component 720, aBWP selector 725, a RACH component 730, a dedicated cause valuetransmitter 735, a MAC CE transmitter 740, and a consistent LBT failuredetermination component 745. Each of these modules may communicate,directly or indirectly, with one another (e.g., via one or more buses).

The switching parameter receiver 710 may receive, from a base station, aBWP switching configuration message including a switching parameter. Insome examples, the switching parameter receiver 710 may determine anumber of BWP switches based on the switching parameter, where theswitch to a second BWP is based on the number of BWP switches. In somecases, the number of BWP switches may include an upper threshold numberof BWP switches, a lower threshold number of BWP switches, a fixednumber of BWP switches, or a combination thereof.

The LBT procedure component 715 may perform a set of LBT procedures fora first BWP.

The BWP switching component 720 may switch to a second BWP for uplinkcommunications with the base station based on the switching parameterand a number of failures associated with the set of LBT procedures forthe first BWP. In some examples, the BWP switching component 720 mayperform one or more LBT procedures for the second BWP and may switch toa third BWP according to the BWP switching configuration and theswitching parameter based on a number of failures associated with theone or more LBT procedures for the second BWP.

The BWP selector 725 may select the second BWP based on the switchingparameter. In some cases, the switching parameter may include anindication of a BWP priority order, where selecting the second BWP isbased on the BWP priority order. Additionally or alternatively, theswitching parameter may include an indication of a subband constraintfor the second BWP, where selecting the second BWP is based on thesubband constraint. In some cases, the second BWP may be wholly in asecond subband different than a first subband of the first BWP, a subsetof the second BWP may be in the second subband different than the firstsubband of the first BWP, or a combination thereof. Additionally oralternatively, the switching parameter may include an indication thatswitching to a same BWP multiple times is permissible, where selectingthe second BWP is based on the indication. Accordingly, the BWP selector725 may determine a time threshold for switching to the same BWP, whereselecting the second BWP is based on a time between successive switchesto the second BWP satisfying the time threshold.

The RACH component 730 may perform a random access procedure on thesecond BWP based on switching to the second BWP. In some examples, theRACH component 730 may transmit a first message of the random accessprocedure, may determine a threshold number of attempts for transmittingthe first message has been satisfied, and may declare an RLF or mayswitch to a third BWP or a combination thereof, based on the thresholdnumber of attempts for transmitting the first message has beensatisfied. Additionally or alternatively, the RACH component 730 maydetermine a number of uplink LBT failures for the second BWP exceeds athreshold value, may switch to a third BWP based on the number of uplinkLBT failures for the second BWP exceeding the threshold value, and mayabort the random access procedure on the second BWP.

The dedicated cause value transmitter 735 may determine that the numberof uplink LBT failures for the first BWP occur on a PSCell. Accordingly,the dedicated cause value transmitter 735 may transmit a dedicated causevalue for the number of uplink LBT failures for the first BWP in an SCGfailure message. In some cases, the dedicated cause value may include anumber of switched BWPs attempted.

The MAC CE transmitter 740 may determine that the number of uplink LBTfailures for the first BWP occur on an SCell and may transmit a MAC CEindicating the uplink LBT failures on a PCell or an additional SCell. Insome examples, the MAC CE transmitter 740 may determine the SCellincludes a set of BWPs that includes the first BWP and may transmit theMAC CE on an additional BWP in a different subband for the SCell thanthe first BWP.

The consistent LBT failure determination component 745 may determine toswitch to the second BWP based on the number of failures associated withthe set of LBT procedures for the first BWP satisfying a thresholdvalue. In some examples, the consistent LBT failure determinationcomponent 745 may perform an MCG recovery procedure via an SN based on adetermination that a number of uplink LBT failures for the second BWPsatisfies the threshold value and that the number of uplink LBT failuresfor the second BWP occurs on a PCell. Additionally, the consistent LBTfailure determination component 745 may transmit an indication of afailure for the PCell based on the number of uplink LBT failures for thesecond BWP exceeding the threshold value to the SN.

FIG. 8 shows a diagram of a system 800 including a device 805 thatsupports uplink LBT failure recovery in accordance with aspects of thepresent disclosure. The device 805 may be an example of or include thecomponents of device 505, device 605, or a UE 115 as described herein.The device 805 may include components for bi-directional voice and datacommunications including components for transmitting and receivingcommunications, including a UE communications manager 810, an I/Ocontroller 815, a transceiver 820, an antenna 825, memory 830, and aprocessor 840. These components may be in electronic communication viaone or more buses (e.g., bus 845).

The UE communications manager 810 may receive, from a base station, aBWP switching configuration message including a switching parameter.Additionally, the UE communications manager 810 may perform a set of LBTprocedures for a first BWP. In some cases, the UE communications manager810 may switch to a second BWP for uplink communications with the basestation based on the switching parameter and a number of failuresassociated with the set of LBT procedures for the first BWP.

The I/O controller 815 may manage input and output signals for thedevice 805. The I/O controller 815 may also manage peripherals notintegrated into the device 805. In some cases, the I/O controller 815may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 815 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. In other cases, the I/O controller 815may represent or interact with a modem, a keyboard, a mouse, atouchscreen, or a similar device. In some cases, the I/O controller 815may be implemented as part of a processor. In some cases, a user mayinteract with the device 805 via the I/O controller 815 or via hardwarecomponents controlled by the I/O controller 815.

The transceiver 820 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described herein. For example, thetransceiver 820 may represent a wireless transceiver and may communicatebi-directionally with another wireless transceiver. The transceiver 820may also include a modem to modulate the packets and provide themodulated packets to the antennas for transmission, and to demodulatepackets received from the antennas.

In some cases, the wireless device may include a single antenna 825.However, in some cases the device may have more than one antenna 825,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 830 may include random-access memory (RAM) and read-onlymemory (ROM). The memory 830 may store computer-readable,computer-executable code 835 including instructions that, when executed,cause the processor to perform various functions described herein. Insome cases, the memory 830 may contain, among other things, a basic I/Osystem (BIOS) which may control basic hardware or software operationsuch as the interaction with peripheral components or devices.

The processor 840 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a central processing unit (CPU), amicrocontroller, an ASIC, an FPGA, a programmable logic device, adiscrete gate or transistor logic component, a discrete hardwarecomponent, or any combination thereof). In some cases, the processor 840may be configured to operate a memory array using a memory controller.In other cases, a memory controller may be integrated into the processor840. The processor 840 may be configured to execute computer-readableinstructions stored in a memory (e.g., the memory 830) to cause thedevice 805 to perform various functions (e.g., functions or taskssupporting uplink LBT failure recovery).

The code 835 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 835 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 835 may not be directly executable by theprocessor 840 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 9 shows a block diagram 900 of a device 905 that supports uplinkLBT failure recovery in accordance with aspects of the presentdisclosure. The device 905 may be an example of aspects of a basestation 105 as described herein. The device 905 may include a receiver910, a base station communications manager 915, and a transmitter 920.The device 905 may also include a processor. Each of these componentsmay be in communication with one another (e.g., via one or more buses).

The receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to uplink LBTfailure recovery, etc.). Information may be passed on to othercomponents of the device 905. The receiver 910 may be an example ofaspects of the transceiver 1220 described with reference to FIG. 12 .The receiver 910 may utilize a single antenna or a set of antennas.

The base station communications manager 915 may transmit, to a UE, a BWPswitching configuration message including a switching parameter. In somecases, the base station communications manager 915 may receive, from theUE, a first uplink transmission in a first BWP. Additionally, the basestation communications manager 915 may receive, from the UE, an uplinktransmission in a second BWP based on the switching parameter and anuplink LBT failure. The base station communications manager 915 may bean example of aspects of the base station communications manager 1210described herein.

The base station communications manager 915, or its sub-components, maybe implemented in hardware, code (e.g., software or firmware) executedby a processor, or any combination thereof. If implemented in codeexecuted by a processor, the functions of the base stationcommunications manager 915, or its sub-components may be executed by ageneral-purpose processor, a DSP, an ASIC, a FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed in the present disclosure.

The base station communications manager 915, or its sub-components, maybe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, the basestation communications manager 915, or its sub-components, may be aseparate and distinct component in accordance with various aspects ofthe present disclosure. In some examples, the base stationcommunications manager 915, or its sub-components, may be combined withone or more other hardware components, including but not limited to anI/O component, a transceiver, a network server, another computingdevice, one or more other components described in the presentdisclosure, or a combination thereof in accordance with various aspectsof the present disclosure.

The transmitter 920 may transmit signals generated by other componentsof the device 905. In some examples, the transmitter 920 may becollocated with a receiver 910 in a transceiver module. For example, thetransmitter 920 may be an example of aspects of the transceiver 1220described with reference to FIG. 12 . The transmitter 920 may utilize asingle antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a device 1005 that supports uplinkLBT failure recovery in accordance with aspects of the presentdisclosure. The device 1005 may be an example of aspects of a device905, or a base station 105 as described herein. The device 1005 mayinclude a receiver 1010, a base station communications manager 1015, anda transmitter 1035. The device 1005 may also include a processor. Eachof these components may be in communication with one another (e.g., viaone or more buses).

The receiver 1010 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to uplink LBTfailure recovery, etc.). Information may be passed on to othercomponents of the device 1005. The receiver 1010 may be an example ofaspects of the transceiver 1220 described with reference to FIG. 12 .The receiver 1010 may utilize a single antenna or a set of antennas.

The base station communications manager 1015 may be an example ofaspects of the base station communications manager 915 as describedherein. The base station communications manager 1015 may include aswitching parameter transmitter 1020, a first BWP receiver 1025, and aswitched BWP receiver 1030. The base station communications manager 1015may be an example of aspects of the base station communications manager1210 described herein.

The switching parameter transmitter 1020 may transmit, to a UE, a BWPswitching configuration message including a switching parameter.

The first BWP receiver 1025 may receive, from the UE, a first uplinktransmission in a first BWP.

The switched BWP receiver 1030 may receive, from the UE, an uplinktransmission in a second BWP based on the switching parameter and anuplink LBT failure.

The transmitter 1035 may transmit signals generated by other componentsof the device 1005. In some examples, the transmitter 1035 may becollocated with a receiver 1010 in a transceiver module. For example,the transmitter 1035 may be an example of aspects of the transceiver1220 described with reference to FIG. 12 . The transmitter 1035 mayutilize a single antenna or a set of antennas.

FIG. 11 shows a block diagram 1100 of a base station communicationsmanager 1105 that supports uplink LBT failure recovery in accordancewith aspects of the present disclosure. The base station communicationsmanager 1105 may be an example of aspects of a base stationcommunications manager 915, a base station communications manager 1015,or a base station communications manager 1210 described herein. The basestation communications manager 1105 may include a switching parametertransmitter 1110, a first BWP receiver 1115, a switched BWP receiver1120, and a LBT failure indication receiver 1125. Each of these modulesmay communicate, directly or indirectly, with one another (e.g., via oneor more buses).

The switching parameter transmitter 1110 may transmit, to a UE, a BWPswitching configuration message including a switching parameter. In somecases, the switching parameter may include a number of BWP switches, anindication of which BWP can be switched to after a failure of anotherBWP, a priority order for a set of BWPs in the BWP switchingconfiguration message, an indication for switching to a BWP in adifferent subband, an indication that a same BWP can be used multipletimes for switching, a threshold time between switching to the same BWP,or a combination thereof.

The first BWP receiver 1115 may receive, from the UE, a first uplinktransmission in a first BWP.

The switched BWP receiver 1120 may receive, from the UE, an uplinktransmission in a second BWP based on the switching parameter and anuplink LBT failure.

The LBT failure indication receiver 1125 may receive, from the UE, adedicated cause value for a number of uplink LBT failures for the firstBWP in an SCG failure message, where the dedicated cause value includesa number of switched BWPs attempted. Additionally or alternatively, theLBT failure indication receiver 1125 may receive, from the UE, a MAC CEindicating a number of uplink LBT failures for the first BWP on a PCellor an SCell. Additionally or alternatively, the LBT failure indicationreceiver 1125 may receive, from an SN, an indication of a failure for aPCell based on a number of uplink LBT failures for the first BWPexceeding a threshold value. In some cases, the MAC CE may be receivedon an additional BWP in a different subband for the secondary cell thanthe first BWP.

FIG. 12 shows a diagram of a system 1200 including a device 1205 thatsupports uplink LBT failure recovery in accordance with aspects of thepresent disclosure. The device 1205 may be an example of or include thecomponents of device 905, device 1005, or a base station 105 asdescribed herein. The device 1205 may include components forbi-directional voice and data communications including components fortransmitting and receiving communications, including a base stationcommunications manager 1210, a network communications manager 1215, atransceiver 1220, an antenna 1225, memory 1230, a processor 1240, and aninter-station communications manager 1245. These components may be inelectronic communication via one or more buses (e.g., bus 1250).

The base station communications manager 1210 may transmit, to a UE, aBWP switching configuration message including a switching parameter. Insome cases, the base station communications manager 1210 may receive,from the UE, a first uplink transmission in a first BWP. Additionally,the base station communications manager 1210 may receive, from the UE,an uplink transmission in a second BWP based on the switching parameterand an uplink LBT failure.

The network communications manager 1215 may manage communications withthe core network (e.g., via one or more wired backhaul links). Forexample, the network communications manager 1215 may manage the transferof data communications for client devices, such as one or more UEs 115.

The transceiver 1220 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described herein. For example, thetransceiver 1220 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1220 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1225.However, in some cases the device may have more than one antenna 1225,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1230 may include RAM, ROM, or a combination thereof. Thememory 1230 may store computer-readable code 1235 including instructionsthat, when executed by a processor (e.g., the processor 1240) cause thedevice to perform various functions described herein. In some cases, thememory 1230 may contain, among other things, a BIOS which may controlbasic hardware or software operation such as the interaction withperipheral components or devices.

The processor 1240 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1240 may be configured to operate a memoryarray using a memory controller. In some cases, a memory controller maybe integrated into processor 1240. The processor 1240 may be configuredto execute computer-readable instructions stored in a memory (e.g., thememory 1230) to cause the device 1205 to perform various functions(e.g., functions or tasks supporting uplink LBT failure recovery).

The inter-station communications manager 1245 may manage communicationswith other base station 105 and may include a controller or schedulerfor controlling communications with UEs 115 in cooperation with otherbase stations 105. For example, the inter-station communications manager1245 may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, the inter-station communications manager1245 may provide an X2 interface within an LTE/LTE-A wirelesscommunication network technology to provide communication between basestations 105.

The code 1235 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1235 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1235 may not be directly executable by theprocessor 1240 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 13 shows a flowchart illustrating a method 1300 that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure. The operations of method 1300 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1300 may be performed by a UE communications manager as describedwith reference to FIGS. 5 through 8 . In some examples, a UE may executea set of instructions to control the functional elements of the UE toperform the functions described. Additionally or alternatively, a UE mayperform aspects of the functions described using special-purposehardware.

At 1305, the UE may receive, from a base station, a BWP switchingconfiguration message including a switching parameter. The operations of1305 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1305 may be performed by aswitching parameter receiver as described with reference to FIGS. 5through 8 .

At 1310, the UE may perform a set of LBT procedures for a first BWP. Theoperations of 1310 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1310 may beperformed by an LBT procedure component as described with reference toFIGS. 5 through 8 .

At 1315, the UE may switch to a second BWP for uplink communicationswith the base station based on the switching parameter and a number offailures associated with the set of LBT procedures for the first BWP.The operations of 1315 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1315may be performed by a BWP switching component as described withreference to FIGS. 5 through 8 .

FIG. 14 shows a flowchart illustrating a method 1400 that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure. The operations of method 1400 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1400 may be performed by a UE communications manager as describedwith reference to FIGS. 5 through 8 . In some examples, a UE may executea set of instructions to control the functional elements of the UE toperform the functions described. Additionally or alternatively, a UE mayperform aspects of the functions described using special-purposehardware.

At 1405, the UE may receive, from a base station, a BWP switchingconfiguration message including a switching parameter. The operations of1405 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1405 may be performed by aswitching parameter receiver as described with reference to FIGS. 5through 8 .

At 1410, the UE may perform a set of LBT procedures for a first BWP. Theoperations of 1410 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1410 may beperformed by an LBT procedure component as described with reference toFIGS. 5 through 8 .

At 1415, the UE may determine a number of BWP switches based on theswitching parameter, where the switch to the second BWP is based on thenumber of BWP switches. The operations of 1415 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1415 may be performed by a switching parameterreceiver as described with reference to FIGS. 5 through 8 .

At 1420, the UE may switch to a second BWP for uplink communicationswith the base station based on the switching parameter and a number offailures associated with the set of LBT procedures for the first BWP.The operations of 1420 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1420may be performed by a BWP switching component as described withreference to FIGS. 5 through 8 .

FIG. 15 shows a flowchart illustrating a method 1500 that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure. The operations of method 1500 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1500 may be performed by a UE communications manager as describedwith reference to FIGS. 5 through 8 . In some examples, a UE may executea set of instructions to control the functional elements of the UE toperform the functions described. Additionally or alternatively, a UE mayperform aspects of the functions described using special-purposehardware.

At 1505, the UE may receive, from a base station, a BWP switchingconfiguration message including a switching parameter. The operations of1505 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1505 may be performed by aswitching parameter receiver as described with reference to FIGS. 5through 8 .

At 1510, the UE may perform a set of LBT procedures for a first BWP. Theoperations of 1510 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1510 may beperformed by an LBT procedure component as described with reference toFIGS. 5 through 8 .

At 1515, the UE may select the second BWP based on the switchingparameter. The operations of 1515 may be performed according to themethods described herein. In some examples, aspects of the operations of1515 may be performed by a BWP selector as described with reference toFIGS. 5 through 8 .

At 1520, the UE may switch to a second BWP for uplink communicationswith the base station based on the switching parameter and a number offailures associated with the set of LBT procedures for the first BWP.The operations of 1520 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1520may be performed by a BWP switching component as described withreference to FIGS. 5 through 8 .

FIG. 16 shows a flowchart illustrating a method 1600 that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure. The operations of method 1600 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1600 may be performed by a UE communications manager as describedwith reference to FIGS. 5 through 8 . In some examples, a UE may executea set of instructions to control the functional elements of the UE toperform the functions described. Additionally or alternatively, a UE mayperform aspects of the functions described using special-purposehardware.

At 1605, the UE may receive, from a base station, a BWP switchingconfiguration message including a switching parameter. The operations of1605 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1605 may be performed by aswitching parameter receiver as described with reference to FIGS. 5through 8 .

At 1610, the UE may perform a set of LBT procedures for a first BWP. Theoperations of 1610 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1610 may beperformed by an LBT procedure component as described with reference toFIGS. 5 through 8 .

At 1615, the UE may switch to a second BWP for uplink communicationswith the base station based on the switching parameter and a number offailures associated with the set of LBT procedures for the first BWP.The operations of 1615 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1615may be performed by a BWP switching component as described withreference to FIGS. 5 through 8 .

At 1620, the UE may perform a random access procedure on the second BWPbased on switching to the second BWP. The operations of 1620 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1620 may be performed by a RACH componentas described with reference to FIGS. 5 through 8 .

FIG. 17 shows a flowchart illustrating a method 1700 that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure. The operations of method 1700 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1700 may be performed by a UE communications manager as describedwith reference to FIGS. 5 through 8 . In some examples, a UE may executea set of instructions to control the functional elements of the UE toperform the functions described. Additionally or alternatively, a UE mayperform aspects of the functions described using special-purposehardware.

At 1705, the UE may receive, from a base station, a BWP switchingconfiguration message including a switching parameter. The operations of1705 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1705 may be performed by aswitching parameter receiver as described with reference to FIGS. 5through 8 .

At 1710, the UE may perform a set of LBT procedures for a first BWP. Theoperations of 1710 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1710 may beperformed by an LBT procedure component as described with reference toFIGS. 5 through 8 .

At 1715, the UE may determine to switch to the second BWP based on thenumber of failures associated with the set of LBT procedures for thefirst BWP satisfying a threshold value. The operations of 1715 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1715 may be performed by a consistent LBTfailure determination component as described with reference to FIGS. 5through 8 .

At 1720, the UE may switch to a second BWP for uplink communicationswith the base station based on the switching parameter and a number offailures associated with the set of LBT procedures for the first BWP.The operations of 1720 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1720may be performed by a BWP switching component as described withreference to FIGS. 5 through 8 .

FIG. 18 shows a flowchart illustrating a method 1800 that supportsuplink LBT failure recovery in accordance with aspects of the presentdisclosure. The operations of method 1800 may be implemented by a basestation 105 or its components as described herein. For example, theoperations of method 1800 may be performed by a base stationcommunications manager as described with reference to FIGS. 9 through 12. In some examples, a base station may execute a set of instructions tocontrol the functional elements of the base station to perform thefunctions described. Additionally or alternatively, a base station mayperform aspects of the functions described using special-purposehardware.

At 1805, the base station may transmit, to a UE, a BWP switchingconfiguration message including a switching parameter. The operations of1805 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1805 may be performed by aswitching parameter transmitter as described with reference to FIGS. 9through 12 .

At 1810, the base station may receive, from the UE, a first uplinktransmission in a first BWP. The operations of 1810 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1810 may be performed by a first BWP receiver asdescribed with reference to FIGS. 9 through 12 .

At 1815, the base station may receive, from the UE, an uplinktransmission in a second BWP based on the switching parameter and anuplink LBT failure. The operations of 1815 may be performed according tothe methods described herein. In some examples, aspects of theoperations of 1815 may be performed by a switched BWP receiver asdescribed with reference to FIGS. 9 through 12 .

It should be noted that the methods described herein describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

The following provides an overview of aspects of the present disclosure:

Aspect 1: A method for wireless communications at a UE, comprising:receiving, from a base station, a bandwidth part switching configurationmessage comprising a switching parameter; performing a plurality oflisten-before-talk procedures for a first bandwidth part; and switchingto a second bandwidth part for uplink communications with the basestation based at least in part on the switching parameter and a numberof failures associated with the plurality of listen-before-talkprocedures for the first bandwidth part.

Aspect 2: The method of aspect 1, further comprising: performing arandom access procedure on the second bandwidth part based at least inpart on switching to the second bandwidth part.

Aspect 3: The method of aspect 2, further comprising: transmitting afirst message of the random access procedure; determining a thresholdnumber of attempts for transmitting the first message has beensatisfied; and declaring a radio link failure or switching to a thirdbandwidth part or a combination thereof based at least in part on thethreshold number of attempts for transmitting the first message has beensatisfied.

Aspect 4: The method of any of aspects 2 through 3, further comprising:determining a number of uplink listen-before-talk failures for thesecond bandwidth part exceeds a threshold value; switching to a thirdbandwidth part based at least in part on the number of uplinklisten-before-talk failures for the second bandwidth part exceeding thethreshold value; and aborting the random access procedure on the secondbandwidth part.

Aspect 5: The method of any of aspects 1 through 4, further comprising:determining that a number of uplink listen-before-talk failures for thefirst bandwidth part occur on a primary secondary cell; and transmittinga dedicated cause value for the number of uplink listen-before-talkfailures for the first bandwidth part in a secondary cell group failuremessage.

Aspect 6: The method of aspect 5, wherein the dedicated cause valuecomprises a number of switched bandwidth parts attempted.

Aspect 7: The method of any of aspects 1 through 6, further comprising:determining that a number of uplink listen-before-talk failures for thefirst bandwidth part occur on a secondary cell; and transmitting amedium access control (MAC) control element indicating the uplinklisten-before-talk failures on a primary cell or an additional secondarycell.

Aspect 8: The method of aspect 7, wherein transmitting the MAC controlelement comprises: determining the secondary cell comprises a pluralityof bandwidth parts that includes the first bandwidth part; andtransmitting the MAC control element on an additional bandwidth part ina different subband for the secondary cell than the first bandwidthpart.

Aspect 9: The method of any of aspects 1 through 8, further comprising:determining to switch to the second bandwidth part based at least inpart on the number of failures associated with the plurality oflisten-before-talk procedures for the first bandwidth part satisfying athreshold value.

Aspect 10: The method of aspect 9, further comprising: performing amaster cell group recovery procedure via a secondary node based at leastin part on a determination that a number of uplink listen-before-talkfailures for the second bandwidth part satisfies the threshold value andthat the number of uplink listen-before-talk failures for the secondbandwidth part occurs on a primary cell.

Aspect 11: The method of aspect 10, wherein performing the master cellgroup recovery procedure via the secondary node comprises: transmittingan indication of a failure for the primary cell based at least in parton the number of uplink listen-before-talk failures for the secondbandwidth part exceeding the threshold value to the secondary node.

Aspect 12: The method of any of aspects 1 through 11, furthercomprising: determining a number of bandwidth part switches based atleast in part on the switching parameter, wherein the switch to thesecond bandwidth part is based at least in part on the number ofbandwidth part switches.

Aspect 13: The method of aspect 12, wherein the switching parametercomprises an indication of one or more of: an upper threshold number ofbandwidth part switches, a lower threshold number of bandwidth partswitches, a fixed number of bandwidth part switches, or a combinationthereof.

Aspect 14: The method of any of aspects 1 through 13, furthercomprising: selecting the second bandwidth part based at least in parton the switching parameter.

Aspect 15: The method of aspect 14, wherein the switching parametercomprises an indication of a bandwidth part priority order, andselecting the second bandwidth part is based at least in part on thebandwidth part priority order.

Aspect 16: The method of any of aspects 14 through 15, wherein theswitching parameter comprises an indication of a subband constraint forthe second bandwidth part, and selecting the second bandwidth part isbased at least in part on the subband constraint.

Aspect 17: The method of aspect 16, wherein the second bandwidth part iswholly in a second subband different than a first subband of the firstbandwidth part, a subset of the second bandwidth part is in the secondsubband different than the first subband of the first bandwidth part, ora combination thereof.

Aspect 18: The method of any of aspects 14 through 17, wherein theswitching parameter comprises an indication that switching to a samebandwidth part multiple times is permissible, and selecting the secondbandwidth part is based at least in part on the indication.

Aspect 19: The method of aspect 18, further comprising: determining atime threshold for switching to the same bandwidth part, whereinselecting the second bandwidth part is based at least in part on a timebetween successive switches to the second bandwidth part satisfying thetime threshold.

Aspect 20: The method of any of aspects 1 through 19, furthercomprising: performing one or more listen-before-talk procedures for thesecond bandwidth part; and switching to a third bandwidth part accordingto the bandwidth part switching configuration message and the switchingparameter based at least in part on a number of failures associated withthe one or more listen-before-talk procedures for the second bandwidthpart.

Aspect 21: A method for wireless communications at a base station,comprising: transmitting, to a UE, a bandwidth part switchingconfiguration message comprising a switching parameter; receiving, fromthe UE, a first uplink transmission in a first bandwidth part; andreceiving, from the UE, an uplink transmission in a second bandwidthpart based at least in part on the switching parameter and an uplinklisten-before-talk failure.

Aspect 22: The method of aspect 21, further comprising: receiving, fromthe UE, a dedicated cause value for a number of uplinklisten-before-talk failures for the first bandwidth part in a secondarycell group failure message, wherein the dedicated cause value comprisesa number of switched bandwidth parts attempted.

Aspect 23: The method of any of aspects 21 through 22, furthercomprising: receiving, from the UE, a medium access control (MAC)control element indicating a number of uplink listen-before-talkfailures for the first bandwidth part on a primary cell or a secondarycell.

Aspect 24: The method of aspect 23, wherein the MAC control element isreceived on an additional bandwidth part in a different subband for thesecondary cell than the first bandwidth part.

Aspect 25: The method of any of aspects 21 through 24, furthercomprising: receiving, from a secondary node, an indication of a failurefor a primary cell based at least in part on a number of uplinklisten-before-talk failures for the first bandwidth part exceeding athreshold value.

Aspect 26: The method of any of aspects 21 through 25, wherein theswitching parameter comprises a number of bandwidth part switches, anindication of which bandwidth part can be switched to after a failure ofanother bandwidth part, a priority order for a plurality of bandwidthparts in the bandwidth part switching configuration message, anindication for switching to a bandwidth part in a different subband, anindication that a same bandwidth part can be used multiple times forswitching, a threshold time between switching to the same bandwidthpart, or a combination thereof.

Aspect 27: An apparatus for wireless communications at a UE, comprisinga processor; memory coupled with the processor; and instructions storedin the memory and executable by the processor to cause the apparatus toperform a method of any of aspects 1 through 20.

Aspect 28: An apparatus for wireless communications at a UE, comprisingat least one means for performing a method of any of aspects 1 through20.

Aspect 29: A non-transitory computer-readable medium storing code forwireless communications at a UE, the code comprising instructionsexecutable by a processor to perform a method of any of aspects 1through 20.

Aspect 30: An apparatus for wireless communications at a base station,comprising a processor; memory coupled with the processor; andinstructions stored in the memory and executable by the processor tocause the apparatus to perform a method of any of aspects 21 through 26.

Aspect 31: An apparatus for wireless communications at a base station,comprising at least one means for performing a method of any of aspects21 through 26.

Aspect 32: A non-transitory computer-readable medium storing code forwireless communications at a base station, the code comprisinginstructions executable by a processor to perform a method of any ofaspects 21 through 26.

Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may bedescribed for purposes of example, and LTE, LTE-A, LTE-A Pro, or NRterminology may be used in much of the description, the techniquesdescribed herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NRnetworks. For example, the described techniques may be applicable tovarious other wireless communications systems such as Ultra MobileBroadband (UMB), Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, aswell as other systems and radio technologies not explicitly mentionedherein.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and components described in connectionwith the disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, a CPU, an FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyprocessor, controller, microcontroller, or state machine. A processormay also be implemented as a combination of computing devices (e.g., acombination of a DSP and a microprocessor, multiple microprocessors, oneor more microprocessors in conjunction with a DSP core, or any othersuch configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein may be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that may beaccessed by a general-purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude RAM, ROM, electrically erasable programmable ROM (EEPROM), flashmemory, compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that may be used to carry or store desired programcode means in the form of instructions or data structures and that maybe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of computer-readable medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an example step that is described as “based on condition A”may be based on both a condition A and a condition B without departingfrom the scope of the present disclosure. In other words, as usedherein, the phrase “based on” shall be construed in the same manner asthe phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “example” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, known structures and devices are shown inblock diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person having ordinaryskill in the art to make or use the disclosure. Various modifications tothe disclosure will be apparent to a person having ordinary skill in theart, and the generic principles defined herein may be applied to othervariations without departing from the scope of the disclosure. Thus, thedisclosure is not limited to the examples and designs described hereinbut is to be accorded the broadest scope consistent with the principlesand novel features disclosed herein.

What is claimed is:
 1. A method for wireless communications at a userequipment (UE), comprising: receiving, from a base station, a bandwidthpart switching configuration message comprising a switching parameter;performing a plurality of listen-before-talk procedures for a firstbandwidth part; and switching to a second bandwidth part for uplinkcommunications with the base station based at least in part on theswitching parameter and a number of failures associated with theplurality of listen-before-talk procedures for the first bandwidth part;performing a random access procedure on the second bandwidth part basedat least in part on switching to the second bandwidth part; transmittinga first message of the random access procedure; determining a thresholdnumber of attempts for transmitting the first message has beensatisfied; and declaring a radio link failure or switching to a thirdbandwidth part or a combination thereof based at least in part on thethreshold number of attempts for transmitting the first message has beensatisfied.
 2. The method of claim 1, further comprising: determining anumber of uplink listen-before-talk failures for the second bandwidthpart exceeds a threshold value; switching to a third bandwidth partbased at least in part on the number of uplink listen-before-talkfailures for the second bandwidth part exceeding the threshold value;and aborting the random access procedure on the second bandwidth part.3. The method of claim 1, further comprising: determining that a numberof uplink listen-before-talk failures for the first bandwidth part occuron a primary secondary cell; and transmitting a dedicated cause valuefor the number of uplink listen-before-talk failures for the firstbandwidth part in a secondary cell group failure message.
 4. The methodof claim 3, wherein the dedicated cause value comprises a number ofswitched bandwidth parts attempted.
 5. The method of claim 1, furthercomprising: determining that a number of uplink listen-before-talkfailures for the first bandwidth part occur on a secondary cell; andtransmitting a medium access control (MAC) control element indicatingthe number of uplink listen-before-talk failures on a primary cell or anadditional secondary cell.
 6. The method of claim 5, whereintransmitting the MAC control element comprises: determining thesecondary cell comprises a plurality of bandwidth parts that includesthe first bandwidth part; and transmitting the MAC control element on anadditional bandwidth part in a different subband for the secondary cellthan the first bandwidth part.
 7. The method of claim 1, furthercomprising: determining to switch to the second bandwidth part based atleast in part on the number of failures associated with the plurality oflisten-before-talk procedures for the first bandwidth part satisfying athreshold value.
 8. The method of claim 7, further comprising:performing a master cell group recovery procedure via a secondary nodebased at least in part on a determination that a number of uplinklisten-before-talk failures for the second bandwidth part satisfies thethreshold value and that the number of uplink listen-before-talkfailures for the second bandwidth part occurs on a primary cell.
 9. Themethod of claim 8, wherein performing the master cell group recoveryprocedure via the secondary node comprises: transmitting an indicationof a failure for the primary cell based at least in part on the numberof uplink listen-before-talk failures for the second bandwidth partexceeding the threshold value to the secondary node.
 10. The method ofclaim 1, further comprising: determining a number of bandwidth partswitches based at least in part on the switching parameter, wherein theswitch to the second bandwidth part is based at least in part on thenumber of bandwidth part switches.
 11. The method of claim 10, whereinthe switching parameter comprises an indication of one or more of: anupper threshold number of bandwidth part switches, a lower thresholdnumber of bandwidth part switches, a fixed number of bandwidth partswitches, or a combination thereof.
 12. The method of claim 1, furthercomprising: selecting the second bandwidth part based at least in parton the switching parameter.
 13. The method of claim 12, wherein theswitching parameter comprises an indication of a bandwidth part priorityorder, and wherein selecting the second bandwidth part is based at leastin part on the bandwidth part priority order.
 14. The method of claim12, wherein the switching parameter comprises an indication of a subbandconstraint for the second bandwidth part, and wherein selecting thesecond bandwidth part is based at least in part on the subbandconstraint.
 15. The method of claim 14, wherein the second bandwidthpart is wholly in a second subband different than a first subband of thefirst bandwidth part, a subset of the second bandwidth part is in thesecond subband different than the first subband of the first bandwidthpart, or a combination thereof.
 16. The method of claim 12, wherein theswitching parameter comprises an indication that switching to a samebandwidth part multiple times is permissible, and wherein selecting thesecond bandwidth part is based at least in part on the indication. 17.The method of claim 16, further comprising: determining a time thresholdfor switching to the same bandwidth part, wherein selecting the secondbandwidth part is based at least in part on a time between successiveswitches to the second bandwidth part satisfying the time threshold. 18.The method of claim 1, further comprising: performing one or morelisten-before-talk procedures for the second bandwidth part; andswitching to a third bandwidth part according to the bandwidth partswitching configuration message and the switching parameter based atleast in part on a number of failures associated with the one or morelisten-before-talk procedures for the second bandwidth part.
 19. Themethod of claim 1, further comprising: switching to a third bandwidthpart based at least in part on the threshold number of attempts fortransmitting the first message has been satisfied.
 20. A method forwireless communications at a base station, comprising: transmitting, toa UE, a bandwidth part switching configuration message comprising aswitching parameter; receiving, from the UE, a first uplink transmissionin a first bandwidth part; receiving, from the UE, an uplinktransmission in a second bandwidth part based at least in part on theswitching parameter and an uplink listen-before-talk failure; andreceiving, from the UE, a medium access control (MAC) control elementindicating a number of uplink listen-before-talk failures for the firstbandwidth part on a primary cell or a secondary cell.
 21. The method ofclaim 20, wherein the MAC control element is received on an additionalbandwidth part in a different subband for the secondary cell than thefirst bandwidth part.
 22. The method of claim 20, further comprising:receiving, from a secondary node, an indication of a failure for aprimary cell based at least in part on the number of uplinklisten-before-talk failures for the first bandwidth part exceeding athreshold value.
 23. The method of claim 19, wherein the switchingparameter comprises a number of bandwidth part switches, an indicationof which bandwidth part can be switched to after a failure of anotherbandwidth part, a priority order for a plurality of bandwidth parts inthe bandwidth part switching configuration message, an indication forswitching to a bandwidth part in a different subband, an indication thata same bandwidth part can be used multiple times for switching, athreshold time between switching to the same bandwidth part, or acombination thereof.
 24. The method of claim 20, further comprising:receiving, from the UE, a dedicated cause value for a number of uplinklisten-before-talk failures for the first bandwidth part in a secondarycell group failure message, wherein the dedicated cause value comprisesa number of switched bandwidth parts attempted.
 25. An apparatus forwireless communications at a user equipment (UE), comprising: aprocessor, memory coupled with the processor; and instructions stored inthe memory and executable by the processor to cause the apparatus to:receive, from a base station, a bandwidth part switching configurationmessage comprising a switching parameter; perform a plurality oflisten-before-talk procedures for a first bandwidth part; switch to asecond bandwidth part for uplink communications with the base stationbased at least in part on the switching parameter and a number offailures associated with the plurality of listen-before-talk proceduresfor the first bandwidth part; transmit a medium access control (MAC)control element indicating a number of uplink listen-before-talkfailures on a primary cell or an additional secondary cell; transmit afirst message of the random access procedure; determine a thresholdnumber of attempts for transmitting the first message has beensatisfied; and declare a radio link failure based at least in part onthe threshold number of attempts for transmitting the first message hasbeen satisfied.
 26. The apparatus of claim 25, wherein the instructionsare further executable by the processor to cause the apparatus to:determine a number of uplink listen-before-talk failures for the secondbandwidth part exceeds a threshold value; switch to a third bandwidthpart based at least in part on the number of uplink listen-before-talkfailures for the second bandwidth part exceeding the threshold value;and abort the random access procedure on the second bandwidth part. 27.The apparatus of claim 25, wherein the instructions are furtherexecutable by the processor to cause the apparatus to: determine that anumber of uplink listen-before-talk failures for the first bandwidthpart occur on a primary secondary cell; and transmit a dedicated causevalue for the number of uplink listen-before-talk failures for the firstbandwidth part in a secondary cell group failure message.
 28. Theapparatus of claim 27, wherein the dedicated cause value comprises anumber of switched bandwidth parts attempted.
 29. The apparatus of claim25, wherein the instructions are further executable by the processor tocause the apparatus to: determine that a number of uplinklisten-before-talk failures for the first bandwidth part occur on asecondary cell; and transmit a medium access control (MAC) controlelement indicating the number of uplink listen-before-talk failures on aprimary cell or an additional secondary cell.
 30. The apparatus of claim29, wherein the instructions to transmit the MAC control element areexecutable by the processor to cause the apparatus to: determine thesecondary cell comprises a plurality of bandwidth parts that includesthe first bandwidth part; and transmit the MAC control element on anadditional bandwidth part in a different subband for the secondary cellthan the first bandwidth part.
 31. The apparatus of claim 25, whereinthe instructions are further executable by the processor to cause theapparatus to: determine to switch to the second bandwidth part based atleast in part on the number of failures associated with the plurality oflisten-before-talk procedures for the first bandwidth part satisfying athreshold value.
 32. The apparatus of claim 31, wherein the instructionsare further executable by the processor to cause the apparatus to:perform a master cell group recovery procedure via a secondary nodebased at least in part on a determination that a number of uplinklisten-before-talk failures for the second bandwidth part satisfies thethreshold value and that the number of uplink listen-before-talkfailures for the second bandwidth part occurs on a primary cell.
 33. Theapparatus of claim 32, wherein the instructions to perform the mastercell group recovery procedure via the secondary node are executable bythe processor to cause the apparatus to: transmit an indication of afailure for the primary cell based at least in part on the number ofuplink listen-before-talk failures for the second bandwidth partexceeding the threshold value to the secondary node.
 34. The apparatusof claim 25, wherein the instructions are further executable by theprocessor to cause the apparatus to: determine a number of bandwidthpart switches based at least in part on the switching parameter, whereinthe switch to the second bandwidth part is based at least in part on thenumber of bandwidth part switches.
 35. The apparatus of claim 34,wherein the switching parameter comprises an indication of one or moreof: comprises an upper threshold number of bandwidth part switches, alower threshold number of bandwidth part switches, a fixed number ofbandwidth part switches, or a combination thereof.
 36. The apparatus ofclaim 25, wherein the instructions are further executable by theprocessor to cause the apparatus to: select the second bandwidth partbased at least in part on the switching parameter.
 37. The apparatus ofclaim 36, wherein the switching parameter comprises an indication of abandwidth part priority order, and wherein selecting the secondbandwidth part is based at least in part on the bandwidth part priorityorder.
 38. The apparatus of claim 36, wherein the switching parametercomprises an indication of a subband constraint for the second bandwidthpart, and wherein selecting the second bandwidth part is based at leastin part on the subband constraint.
 39. The apparatus of claim 38,wherein the second bandwidth part is wholly in a second subbanddifferent than a first subband of the first bandwidth part, a subset ofthe second bandwidth part is in the second subband different than thefirst subband of the first bandwidth part, or a combination thereof. 40.The apparatus of claim 36, wherein the switching parameter comprises anindication that switching to a same bandwidth part multiple times ispermissible, and wherein selecting the second bandwidth part is based atleast in part on the indication.
 41. The apparatus of claim 40, whereinthe instructions are further executable by the processor to cause theapparatus to: determine a time threshold for switching to the samebandwidth part, wherein selecting the second bandwidth part is based atleast in part on a time between successive switches to the secondbandwidth part satisfying the time threshold.
 42. The apparatus of claim25, wherein the instructions are further executable by the processor tocause the apparatus to: perform one or more listen-before-talkprocedures for the second bandwidth part; and switch to a thirdbandwidth part according to the bandwidth part switching configurationmessage and the switching parameter based at least in part on a numberof failures associated with the one or more listen-before-talkprocedures for the second bandwidth part.
 43. The apparatus of claim 25,wherein the instructions are further executable by the processor tocause the apparatus to: switch to a third bandwidth part based at leastin part on the threshold number of attempts for transmitting the firstmessage has been satisfied.
 44. An apparatus for wireless communicationsat a base station, comprising: a processor, memory coupled with theprocessor; and instructions stored in the memory and executable by theprocessor to cause the apparatus to: transmit, to a UE, a bandwidth partswitching configuration message comprising a switching parameter;receive, from the UE, a first uplink transmission in a first bandwidthpart; receive, from the UE, an uplink transmission in a second bandwidthpart based at least in part on the switching parameter and an uplinklisten-before-talk failure; and receive, from the UE, a medium accesscontrol (MAC) control element indicating a number of uplinklisten-before-talk failures for the first bandwidth part on a primarycell or a secondary cell.
 45. The apparatus of claim 44, wherein the MACcontrol element is received on an additional bandwidth part in adifferent subband for the secondary cell than the first bandwidth part.46. The apparatus of claim 44, wherein the instructions are furtherexecutable by the processor to cause the apparatus to: receive, from asecondary node, an indication of a failure for a primary cell based atleast in part on the number of uplink listen-before-talk failures forthe first bandwidth part exceeding a threshold value.
 47. The apparatusof claim 44, wherein the switching parameter comprises a number ofbandwidth part switches, an indication of which bandwidth part can beswitched to after a failure of another bandwidth part, a priority orderfor a plurality of bandwidth parts in the bandwidth part switchingconfiguration message, an indication for switching to a bandwidth partin a different subband, an indication that a same bandwidth part can beused multiple times for switching, a threshold time between switching tothe same bandwidth part, or a combination thereof.
 48. The apparatus ofclaim 44, wherein the instructions are further executable by theprocessor to cause the apparatus to: receive, from the UE, a dedicatedcause value for a number of uplink listen-before-talk failures for thefirst bandwidth part in a secondary cell group failure message, whereinthe dedicated cause value comprises a number of switched bandwidth partsattempted.